CCNA MPLS Operations Questions — Page 1 of 2

Multi-Selectmedium

Which TWO statements about MPLS label imposition (push) are true? (Choose TWO.)

Select 2 answers

A.Label imposition occurs at the ingress LSR.

B.Label imposition occurs at the egress LSR.

C.The imposed label is determined by the Forwarding Equivalence Class (FEC).

D.The imposed label is always the top label in a label stack.

E.Label imposition is performed using the 'tag-switching' command.

AnswersA, C

The ingress LSR pushes a label onto an incoming IP packet to begin MPLS forwarding.

Why this answer

Label imposition occurs at the ingress LSR, which pushes a label onto an unlabeled IP packet. The label is based on the FEC (Forwarding Equivalence Class) derived from the IP destination. The egress LSR pops the label, not imposes it.

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MCQeasy

A network engineer runs the following command on Router R1: R1# show ip sla statistics 1 IPSLAs Latest Operation Statistics IPSLA operation id: 1 Type of operation: icmp-echo Latest RTT: 10 milliseconds Latest operation start time: 00:15:30 UTC Mon Mar 1 2021 Latest operation return code: OK Number of successes: 100 Number of failures: 0 Operation time to live: Forever Based on this output, which statement is correct?

A.The IP SLA operation has failed 100 times.

B.The IP SLA operation is successful and has a low RTT.

C.The IP SLA operation type is udp-jitter.

D.The IP SLA operation has expired.

AnswerB

Return code OK, RTT 10 ms, 100 successes.

Why this answer

The output shows an IP SLA operation of type icmp-echo with a return code 'OK', 100 successes, and 0 failures. This indicates the operation is functioning correctly.

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MCQhard

An engineer configures MPLS forwarding on a router. The MPLS LDP neighbors are established, but some prefixes are not being assigned labels. The engineer checks the 'show mpls ldp bindings' and sees that the prefixes are missing. What is the most likely explanation?

A.The prefix is learned via BGP, and LDP does not assign labels to BGP routes by default.

B.The 'mpls ldp advertise-labels' command is configured to deny the prefix.

C.The 'mpls ldp label' command is missing on the interface.

D.The 'tag-switching' is not enabled globally.

AnswerA

LDP by default only assigns labels to IGP routes (OSPF, EIGRP, IS-IS). BGP routes are not labeled unless 'mpls ldp autoconfig bgp' or 'label-distribution' is configured for BGP.

Why this answer

MPLS LDP assigns labels to prefixes that are in the routing table and are IGP routes. If a prefix is learned via BGP, LDP will not assign a label to it by default unless the 'mpls ldp autoconfig' or 'label-distribution' is configured for BGP. Additionally, if the prefix is a connected route or a static route, LDP may not assign a label unless explicitly configured.

The edge case is that the prefix is a BGP route, and LDP does not label BGP routes by default.

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Multi-Selecthard

Which THREE statements about MPLS label operations (push, swap, pop) are true? (Choose THREE.)

Select 3 answers

A.The ingress LSR performs a label push operation.

B.The transit LSR performs a label swap operation.

C.The egress LSR always performs a label pop operation.

D.The penultimate hop router (PHP) performs a label pop operation.

E.Label operations are determined by the IP routing table.

AnswersA, B, D

The ingress LSR adds a label to an unlabeled IP packet to begin MPLS forwarding.

Why this answer

In MPLS, the ingress LSR pushes a label, transit LSRs swap labels, and the penultimate hop router (PHP) pops the label. The egress LSR does not perform label operations if PHP is used. Label operations are based on the label forwarding table, not the routing table directly.

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MCQhard

A network engineer is troubleshooting an MPLS L3VPN where CE1 can ping the PE1 interface but cannot ping CE2. On PE1, show ip route vrf CUSTOMER shows the route to CE2's subnet, but show bgp vpnv4 unicast all neighbors 10.0.0.2 advertised-routes does not show the route. The BGP session between PE1 and PE2 is established. What is the most likely cause?

A.The VRF export route-target does not match the import route-target on the remote PE.

B.A route-map applied to the VRF export is filtering the route.

C.The BGP session is not using the correct update-source.

D.The next-hop-self command is missing under the VRF address-family.

AnswerB

Correct because a route-map on VRF export can filter routes before they are advertised to BGP, preventing the route from being sent to the remote PE.

Why this answer

The route is present in the VRF but not advertised to the remote PE, indicating a BGP policy issue. Since the BGP session is up, the most likely cause is that the route is not being redistributed into BGP or is being filtered by a route-map or prefix-list on the VRF export.

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MCQmedium

Examine the following partial MPLS configuration on a Cisco IOS-XE router: interface GigabitEthernet0/0 ip address 10.0.1.1 255.255.255.252 mpls ip mpls label protocol ldp ! router ospf 1 network 10.0.1.0 0.0.0.3 area 0 ! mpls ldp router-id Loopback0 force What is the effect of this configuration?

A.LDP will establish a session with the neighbor on GigabitEthernet0/0, using Loopback0 as the transport address.

B.LDP will use the IP address of GigabitEthernet0/0 as the router ID because 'force' is not valid.

C.LDP sessions will fail because OSPF is not redistributed into LDP.

D.MPLS forwarding will not occur because 'mpls label protocol ldp' is redundant and causes a conflict.

AnswerA

The 'mpls ldp router-id Loopback0 force' command forces LDP to use Loopback0 as the router ID, which becomes the transport address for LDP sessions. The 'mpls ip' on the interface enables label switching and LDP hello messages.

Why this answer

The configuration enables LDP on the interface and globally via 'mpls ip'. The 'mpls label protocol ldp' is default but explicit. The 'mpls ldp router-id Loopback0 force' ensures LDP uses Loopback0 as the router ID, overriding any other interface.

OSPF advertises the /30 link. This is a correct minimal MPLS configuration.

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MCQhard

A network engineer runs the following command to debug MPLS LDP errors: R1# debug mpls ldp errors Output: *Mar 1 00:01:23.456: LDP: Received malformed hello from 10.0.0.2 *Mar 1 00:01:23.789: LDP: Received malformed initialization from 10.0.0.2 *Mar 1 00:01:24.012: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN What does this output indicate?

A.The LDP session with 10.0.0.2 failed due to malformed messages from the neighbor

B.The LDP session with 10.0.0.2 is up and stable

C.R1 is sending malformed messages to 10.0.0.2

D.The LDP session is using incorrect transport address

AnswerA

Malformed messages were received, leading to session teardown.

Why this answer

The debug output shows LDP errors. R1 received malformed hello and initialization messages from neighbor 10.0.0.2, causing the LDP session to go down. This indicates a configuration mismatch or software bug on the neighbor.

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MCQmedium

A network engineer runs the following command to troubleshoot an MPLS Operations issue: R1# debug mpls ldp transport 10.1.1.1 Output: *Mar 1 00:01:23.456: LDP: Sent hello to 10.1.1.1 (UDP 646) on GigabitEthernet0/0 *Mar 1 00:01:23.789: LDP: Received hello from 10.1.1.1 (UDP 646) on GigabitEthernet0/0 *Mar 1 00:01:24.012: LDP: Opened TCP connection to 10.1.1.1:646 *Mar 1 00:01:24.345: LDP: Initialization msg sent to 10.1.1.1 *Mar 1 00:01:24.678: LDP: Initialization msg received from 10.1.1.1 *Mar 1 00:01:25.001: LDP: Session with 10.1.1.1:0 (0x1234) is UP What does this output indicate?

A.LDP session with neighbor 10.1.1.1 is successfully established

B.LDP discovery via multicast hello failed

C.TCP connection to 10.1.1.1 was refused

D.LDP session is stuck in initialization state

AnswerA

The output shows all steps of LDP session establishment completing successfully, ending with session UP.

Why this answer

The debug output shows the LDP transport session establishment process. The sequence of events indicates a successful LDP session establishment: hello exchange, TCP connection, initialization messages, and session UP.

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MCQmedium

A network engineer runs the following command to verify MPLS LDP discovery sources: R1# show mpls ldp discovery detail Output: Local LDP Identifier: 10.0.0.1:0 Discovery Sources: Interfaces: GigabitEthernet0/0 (hello interval 5 s, targeted hello interval 10 s) LDP Id: 10.0.0.2:0, transport address: 10.0.0.2 Hold time: 15 s (local: 15, peer: 15) GigabitEthernet0/1 (hello interval 5 s, targeted hello interval 10 s) LDP Id: 10.0.0.3:0, transport address: 10.0.0.3 Hold time: 15 s (local: 15, peer: 15) What does this output indicate?

A.R1 has discovered two LDP neighbors via link hellos on two different interfaces

B.R1 is using targeted hellos only

C.R1 has no LDP neighbors

D.The LDP session with 10.0.0.2 is down

AnswerA

The output shows two interfaces with LDP neighbors discovered via link hellos.

Why this answer

The output shows LDP discovery sources. R1 has discovered two LDP neighbors via link hellos on interfaces GigabitEthernet0/0 and GigabitEthernet0/1. Both neighbors have a hold time of 15 seconds.

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MCQmedium

In MPLS LDP, what is the default label retention mode on Cisco IOS-XE routers?

A.Liberal Label Retention mode

B.Conservative Label Retention mode

C.Ordered Label Retention mode

D.Independent Label Retention mode

AnswerA

Liberal retention is the default; it allows faster convergence but uses more memory.

Why this answer

The default label retention mode is Liberal, meaning that a router retains all label bindings received from neighbors, even if the neighbor is not the next hop for the FEC.

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MCQmedium

Which of the following statements about MPLS label imposition and disposition is true?

A.The egress LER always performs the label pop operation.

B.The ingress LER performs the label push operation, and the egress LER performs the label pop operation unless PHP is used.

C.The penultimate hop router always pushes an additional label.

D.Label disposition occurs only at the ingress LER.

AnswerB

Standard MPLS operation: ingress pushes, egress pops. PHP allows the penultimate hop to pop, so the egress does not need to.

Why this answer

In MPLS, the ingress LER (Label Edge Router) imposes a label on the packet (push operation). The egress LER removes the label (pop operation). The penultimate hop router may perform penultimate hop popping (PHP) to remove the label before the egress, reducing the egress's workload.

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MCQhard

An engineer configures Control Plane Policing (CoPP) on a router to protect the control plane. After applying the policy, the router becomes unreachable via SSH and SNMP. The engineer checks the policy and confirms that the class-map for SSH and SNMP traffic is set to 'permit'. What is the most likely explanation?

A.The class-default is set to 'drop', causing all unmatched traffic to be dropped, including SSH and SNMP if they are not correctly classified.

B.The 'rate-limit' is configured in bps instead of pps, causing excessive policing.

C.The 'service-policy' is applied to the control-plane input direction, but SSH and SNMP are output traffic.

D.The class-map for SSH and SNMP uses a 'match-all' condition, but the access-list has multiple entries that are ORed.

AnswerA

In CoPP, the class-default is the default class for all traffic not matched by other classes. If it is set to drop, any traffic that does not match the explicit classes will be dropped. If SSH or SNMP traffic is not correctly matched by the class-map (e.g., due to a typo in the access-list), it will fall into class-default and be dropped.

Why this answer

A common edge case with CoPP is that the default class class-default is often set to 'drop' or 'police' with a very low rate, which can drop all traffic not explicitly matched by other classes. Even if SSH and SNMP are permitted, if the class-default is set to drop, any traffic that does not match the explicit classes (e.g., due to a misclassification) will be dropped. Additionally, the order of class-maps matters; if a broader class matches before the specific one, the traffic may be policed incorrectly.

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MCQeasy

What is the default behavior of LDP when establishing a session between two directly connected routers?

A.LDP sends hellos to the unicast address of each neighbor.

B.LDP uses TCP port 646 for session establishment and UDP port 646 for hellos.

C.LDP hellos are sent to the all-OSPF-routers multicast address 224.0.0.5.

D.LDP sessions are established using UDP for reliability.

AnswerB

LDP uses UDP port 646 for hello messages (discovery) and TCP port 646 for session establishment and label exchange.

Why this answer

LDP uses hello messages to discover neighbors. By default, LDP hellos are sent to the multicast address 224.0.0.2 (all routers) on the local link. The session is established using the transport address, which by default is the router ID (usually the highest loopback or interface IP).

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MCQmedium

A network engineer runs the following command on Router R1: R1# show ip nhrp 10.0.0.2/32 via 10.0.0.2, Tunnel0 created 00:15:30, expire 01:44:30 Type: dynamic, Flags: used NBMA address: 192.168.1.2 10.0.0.3/32 via 10.0.0.3, Tunnel0 created 00:10:20, expire 01:49:40 Type: dynamic, Flags: used NBMA address: 192.168.1.3 Based on this output, which statement is correct?

A.Both NHRP entries are static.

B.Both NHRP entries are active and dynamically learned.

C.The NHRP entries have expired.

D.The NBMA addresses are IPv6 addresses.

AnswerB

Type dynamic and flags used indicate active dynamic entries.

Why this answer

The output shows two NHRP entries with 'Type: dynamic', meaning they were learned dynamically (not statically configured). Both have 'Flags: used', indicating they are active. The expiration times show they will expire in about 1 hour 44 minutes and 1 hour 49 minutes, respectively.

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MCQhard

An engineer configures BGP between two iBGP peers in the same AS. The engineer sets 'next-hop-self' on the neighbor statement. However, the routes received from the iBGP peer still show the original next-hop as unreachable. What is the most likely explanation?

A.The 'next-hop-self' command was applied under the wrong address-family.

B.The 'next-hop-self' command is not supported for iBGP peers.

C.The 'synchronization' command is enabled, causing the next-hop to be preserved.

D.The 'bgp bestpath as-path multipath-relax' command is interfering.

AnswerA

In BGP, 'next-hop-self' can be configured per address-family. If it is applied under the IPv4 unicast address-family but the routes are being exchanged in a different address-family (e.g., VPNv4), it will not take effect.

Why this answer

The 'next-hop-self' command in BGP modifies the next-hop attribute for routes advertised to the neighbor. However, if the route is received from an eBGP peer and then advertised to an iBGP peer, the next-hop is changed only for the iBGP peer if 'next-hop-self' is configured. But if the iBGP peer is also a route reflector client, the route reflector does not change the next-hop unless 'next-hop-self' is configured on the route reflector itself.

The edge case here is that the engineer may have configured 'next-hop-self' on the wrong router or the command is applied to the wrong address-family.

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MCQhard

A network engineer is troubleshooting MPLS traffic engineering (TE) tunnels. A TE tunnel from Router A to Router B is configured but remains down. The engineer runs show mpls traffic-eng tunnels and sees that the tunnel is in 'down' state with the error 'Path computation failed'. The IGP is OSPF with MPLS TE enabled, and the network is fully meshed. What is the most likely root cause?

A.MPLS TE is not enabled on all interfaces along the path.

B.The tunnel destination is not reachable via the IGP.

C.RSVP is not configured on the tunnel interface.

D.The tunnel bandwidth is set too high, exceeding available bandwidth.

AnswerA

Correct because MPLS TE must be enabled on each interface to advertise link attributes into the TED; otherwise, the headend cannot compute a constraint-based path.

Why this answer

The 'Path computation failed' error indicates that the headend router cannot find a path meeting the constraints. Since OSPF TE is enabled, the issue is likely that the traffic engineering database (TED) is incomplete because MPLS TE is not enabled on all intermediate interfaces, preventing the headend from learning link attributes.

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MCQhard

EIGRP stuck-in-active (SIA) occurs in a large network. Router R1 shows 'show ip eigrp topology 10.0.0.0/24' output: 'P 10.0.0.0/24, 1 successors, FD is 128000, Q is 0, SIA is 00:01:00' and 'show ip eigrp neighbors' shows neighbor R2 in state 'Active'. R1 configuration includes 'router eigrp 100 network 10.0.0.0 passive-interface default'. What is the root cause?

A.R2 has 'passive-interface default' configured, which prevents it from sending query replies back to R1.

B.R1 has a route-map that filters the query for prefix 10.0.0.0/24.

C.The EIGRP K-values mismatch between R1 and R2 causes neighbor relationship issues.

D.The network 10.0.0.0 is not directly connected; need redistribution.

AnswerA

Passive interface on R2 blocks EIGRP packets, including replies, causing SIA on R1.

Why this answer

EIGRP SIA occurs when a query is not replied within the active timer. The 'passive-interface default' command makes all interfaces passive, preventing EIGRP hellos and queries from being sent on those interfaces. If R1 has a passive interface to R2, no queries are sent, but if R1 is the query originator and R2 is not responding due to passive interface on R2's side, SIA can occur.

However, the scenario shows R1's neighbor R2 is in Active state, meaning R1 sent a query to R2 but R2 did not reply. This could be because R2 has a passive interface to R1, blocking the query reply.

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Drag & Drophard

Drag and drop the steps for troubleshooting MPLS operations adjacency or connectivity failures into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Start by verifying LDP neighbor state, then check interface MPLS enablement, inspect label bindings, test end-to-end LSP connectivity, and finally validate TTL propagation for troubleshooting.

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MCQhard

A network engineer runs the following command on Router R1: R1# show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or Tunnel Id Switched interface 16 Pop Label 10.1.1.0/24 0 Gi0/0 192.168.1.2 17 21 10.2.2.0/24 1500 Gi0/0 192.168.1.2 18 Untagged 10.3.3.0/24 0 Gi0/1 192.168.2.2 Based on this output, what is the problem with the label entry for 10.3.3.0/24?

A.The label 18 is being swapped correctly.

B.The prefix 10.3.3.0/24 is being forwarded with MPLS label 18.

C.The next-hop router 192.168.2.2 is not an LDP neighbor for this prefix.

D.The label 18 is being popped by the next-hop router.

AnswerC

'Untagged' indicates the next hop did not provide a label.

Why this answer

The entry for 10.3.3.0/24 shows 'Untagged' in the outgoing label column, meaning the router is forwarding IP packets without an MPLS label. This indicates that the next-hop router (192.168.2.2) did not assign a label for this prefix, possibly because LDP is not enabled on that interface or the neighbor is not an LDP peer.

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MCQhard

CoPP (Control Plane Policing) rate-limit impacts legitimate traffic. Router R1 has CoPP policy applied: 'class-map match-all BGP class-map match-all SSH match protocol bgp match protocol ssh policy-map COPP class BGP police 10000 conform-action transmit exceed-action drop'. Network engineers cannot SSH to R1, but BGP sessions are stable. 'show policy-map control-plane' output shows 'BGP class: 0 packets, 0 bytes' and 'SSH class: 0 packets, 0 bytes'. What is the root cause?

A.The class-map uses 'match-all' instead of 'match-any', causing SSH traffic not to match the class and be dropped by default action.

B.The police rate is too low for SSH traffic; need to increase.

C.ACL on the interface blocks SSH before CoPP is applied.

D.CoPP is applied to the wrong direction; should be input.

AnswerA

With match-all, a packet must be both BGP and SSH, which is impossible; SSH packets go to default class, likely drop.

Why this answer

The class-map uses 'match protocol bgp' and 'match protocol ssh' with match-all, meaning both conditions must be true for a packet to match. SSH packets do not match protocol bgp, so they fall through to the default class, which may have a drop policy. The class-map should be match-any or separate classes for each protocol.

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MCQhard

A network engineer runs the following command to examine MPLS LDP neighbor details: R1# show mpls ldp neighbor detail Output: Peer LDP Ident: 10.0.0.2:0; Local LDP Ident 10.0.0.1:0 TCP connection: 10.0.0.2.646 - 10.0.0.1.55432 State: Oper; Msgs sent/rcvd: 123/456; Downstream on demand Up time: 1w2d LDP discovery sources: GigabitEthernet0/0, hello interval: 5 s, targeted: no Addresses bound to peer LDP Ident: 10.0.0.2 10.0.1.2 192.168.1.1 What does this output indicate?

A.The LDP session with 10.0.0.2 is operational and was discovered via link hello on GigabitEthernet0/0

B.The LDP session is using targeted hello

C.The LDP session has been up for 1 minute and 2 seconds

D.The neighbor is using downstream-on-demand label advertisement mode

AnswerA

State is Oper, and discovery source is GigabitEthernet0/0 with no targeted hello.

Why this answer

The output shows detailed LDP neighbor information. The session is operational (State: Oper) for 1 week 2 days. The neighbor is directly connected via GigabitEthernet0/0 (non-targeted hello).

The peer has multiple addresses bound to its LDP identifier.

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MCQmedium

Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.252 mpls ip ! interface GigabitEthernet0/1 ip address 10.0.1.1 255.255.255.252 mpls ip ! router ospf 1 network 10.0.0.0 0.0.0.3 area 0 network 10.0.1.0 0.0.0.3 area 0 ! mpls ldp router-id Loopback0 force ! interface Loopback0 ip address 192.168.0.1 255.255.255.255 What will happen when this router attempts to establish an LDP session with a neighbor on GigabitEthernet0/0?

A.LDP will use the IP address of GigabitEthernet0/0 as the transport address because Loopback0 is not in OSPF.

B.LDP will use Loopback0 (192.168.0.1) as the transport address, but the neighbor must have a route to 192.168.0.1 for the session to establish.

C.LDP will not use Loopback0 because the interface is not configured with 'mpls ip'.

D.LDP will use the IP address of GigabitEthernet0/1 because it has the highest IP among MPLS-enabled interfaces.

AnswerB

The 'force' keyword sets the LDP router ID to Loopback0. However, the loopback is not included in the OSPF network statements, so the neighbor may not have reachability to 192.168.0.1, causing LDP session failure. This is a common misconfiguration.

Why this answer

The configuration is correct. LDP will use Loopback0 (192.168.0.1) as its router ID and transport address. The neighbor must be able to reach 192.168.0.1 via the IGP.

Since OSPF advertises the loopback, it should work. The question tests understanding of LDP transport address usage.

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MCQeasy

Which LDP message type is used to request label bindings from a neighbor?

A.Label Request message

B.Label Mapping message

C.Label Withdraw message

D.Label Release message

AnswerA

The Label Request message is used to request label bindings for a FEC.

Why this answer

The Label Request message is sent by an LDP router to request a label binding for a specific FEC from its neighbor.

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Multi-Selecthard

Which TWO statements correctly describe the behavior of TTL propagation in MPLS networks? (Choose TWO.)

Select 2 answers

A.Disabling TTL propagation prevents traceroute from revealing the internal LSR hops.

B.The command 'no mpls ip propagate-ttl' is used to disable TTL propagation on a Cisco IOS router.

C.The command 'no mpls ip ttl-propagate' is used to disable TTL propagation.

D.When TTL propagation is disabled, traceroute shows every LSR hop in the MPLS core.

E.When TTL propagation is disabled, the TTL value is decremented normally at each LSR hop.

AnswersA, B

Correct. With TTL propagation disabled, traceroute shows only the ingress and egress LSRs, hiding the core.

Why this answer

In MPLS, TTL propagation can be disabled for security or to hide the core topology. When disabled, the IP TTL is copied to the MPLS label only at the ingress LSR, and at the egress LSR the MPLS TTL is copied back to the IP header. By default, TTL propagation is enabled.

The command 'no mpls ip propagate-ttl' disables it. Option A is correct because disabling TTL propagation hides the core hops from traceroute. Option B is correct because the command to disable is indeed 'no mpls ip propagate-ttl'.

Option C is false: the command is not 'no mpls ip ttl-propagate'. Option D is false: traceroute shows only the ingress and egress LSRs, not all hops. Option E is false: when disabled, the TTL is not decremented across the MPLS core.

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MCQhard

Which MPLS label value is reserved for the Explicit NULL label and what is its purpose?

A.Label 0; used for the Explicit NULL label to indicate that the penultimate hop should pop the label.

B.Label 1; used for the Router Alert label.

C.Label 2; used for the Implicit NULL label.

D.Label 3; used for the Implicit NULL label.

AnswerA

Label 0 is the IPv4 Explicit NULL per RFC 3032.

Why this answer

Label value 0 is the IPv4 Explicit NULL label, used to signal the penultimate hop to pop the label stack and forward the packet based on the IP header.

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MCQmedium

A network engineer is troubleshooting an MPLS L2VPN (VPWS) where the pseudowire between two PE routers is down. The show mpls l2transport vc command displays state 'down' and the VC ID is correct on both ends. The engineer checks the MPLS LDP session and sees it is up, but the targeted LDP session for the pseudowire is not established. What is the most likely cause?

A.The mpls ldp neighbor command is missing on one or both PEs.

B.The VC ID does not match on both ends.

C.The IGP is not converging, causing reachability issues.

D.The mpls label protocol ldp command is missing globally.

AnswerA

Correct because targeted LDP sessions require explicit configuration using the mpls ldp neighbor command to initiate the session for pseudowire signaling.

Why this answer

For a pseudowire to be established, a targeted LDP session is required between the two PE routers. If the targeted LDP session is not established, the pseudowire cannot exchange labels. The most common cause is that the mpls ldp neighbor command is missing or misconfigured on one or both PEs.

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MCQhard

An engineer configures EIGRP named mode on a router. The neighbor adjacency forms, but the router does not install any routes from the neighbor. The engineer checks and confirms that the neighbor is not configured as a stub. What is the most likely explanation?

A.The 'default-information' is not allowed in named mode by default, so default routes are not accepted.

B.The 'af-interface' has 'split-horizon' enabled by default, preventing the neighbor from advertising routes learned from the same interface.

C.The 'metric weights' are mismatched between the two routers.

D.The 'log-neighbor-changes' command is missing, causing route installation to be suppressed.

AnswerB

In EIGRP named mode, split horizon is enabled by default on the af-interface. If the neighbor is reachable via the same interface that the router uses to send updates, split horizon can block the neighbor from advertising routes back, causing no routes to be installed.

Why this answer

In EIGRP named mode, the default behavior for the 'af-interface' is to have 'no passive-interface' but the default for 'hello-interval' and 'hold-time' may differ from classic mode. However, a common edge case is that the 'af-interface' default for 'split-horizon' is enabled, which can prevent the neighbor from advertising routes back if the same interface is used for multiple neighbors. But the key issue here is that named mode uses a different default for 'default-information'—it is not allowed unless explicitly configured, and the neighbor may be sending a default route that is not accepted.

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MCQmedium

Given the following configuration: ip cef ! interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.252 mpls ip ! interface GigabitEthernet0/1 ip address 10.2.2.1 255.255.255.252 mpls ip ! router ospf 1 network 10.0.0.0 0.255.255.255 area 0 ! mpls ldp router-id Loopback0 force ! interface Loopback0 ip address 192.168.0.1 255.255.255.255 A network engineer notices that LDP sessions are not establishing. What is the most likely cause?

A.The OSPF network statement is too broad and causes routing issues.

B.The LDP router ID is not reachable because the loopback is not advertised in OSPF.

C.The 'mpls ip' command is missing on Loopback0.

D.The 'force' keyword prevents LDP from using any other interface if Loopback0 is down.

AnswerB

The loopback 192.168.0.1 is not in the OSPF domain, so neighbors cannot route to it. LDP uses the router ID as the transport address, and without reachability, sessions cannot establish.

Why this answer

The loopback is not advertised in OSPF because the network statement 10.0.0.0 0.255.255.255 does not include 192.168.0.1. The neighbor cannot reach the LDP router ID, so LDP sessions fail. This is a common oversight.

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MCQhard

An engineer configures mutual redistribution between OSPF and EIGRP on a router. After the configuration, a routing loop occurs for a specific prefix. The engineer checks and confirms that route tagging is not used. What is the most likely explanation?

A.The redistribution is not filtered, so the same prefix is redistributed back and forth, causing a loop.

B.The 'default-metric' command is missing in both protocols, causing the seed metric to be inconsistent.

C.The 'subnets' keyword is missing in the OSPF redistribution command.

D.The 'distance' command is used to change AD, causing OSPF and EIGRP to have the same AD.

AnswerA

Without route tagging or filtering, mutual redistribution can lead to a feedback loop where a route redistributed from OSPF to EIGRP is then redistributed back into OSPF, creating a loop.

Why this answer

Without route tagging, mutual redistribution can cause a routing loop when the same prefix is redistributed back and forth. The edge case is that OSPF and EIGRP have different administrative distances (AD). OSPF external routes have AD 110, and EIGRP external routes have AD 170.

If the prefix is learned via both protocols, the router prefers the lower AD (OSPF external). However, if the router redistributes the EIGRP route into OSPF, and then receives it back via OSPF, it may prefer the OSPF route and cause a loop. The loop is exacerbated if the redistribution is not filtered.

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MCQmedium

Given the following partial configuration: ip cef ! interface Loopback0 ip address 10.0.0.1 255.255.255.255 ! interface GigabitEthernet0/0 ip address 10.1.1.1 255.255.255.252 mpls ip ! router ospf 1 network 10.0.0.1 0.0.0.0 area 0 network 10.1.1.0 0.0.0.3 area 0 ! mpls ldp router-id Loopback0 force What is missing from this configuration to ensure proper MPLS LDP operation?

A.The 'mpls label protocol ldp' command is missing globally or on the interface.

B.The 'mpls ldp neighbor' command is needed to specify the neighbor's IP address.

C.Nothing is missing; the configuration is complete for basic MPLS LDP operation.

D.The 'mpls ip' command must also be applied under the OSPF process.

AnswerC

All required components are present: CEF, interface MPLS enablement, IGP for reachability, and a stable LDP router ID.

Why this answer

The configuration appears correct: CEF enabled, MPLS enabled on the interface, OSPF advertising all networks, and LDP router-id set to a loopback. There is no missing element for basic LDP operation. However, some might think 'mpls label protocol ldp' is needed, but it is default.

The question tests if the candidate can identify that nothing is missing.

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Multi-Selecthard

Which TWO statements about MPLS label imposition, disposition, and swapping are true? (Choose TWO.)

Select 2 answers

A.Penultimate Hop Popping (PHP) reduces the processing load on the egress LSR by having the penultimate LSR pop the label.

B.An intermediate LSR performs a label swap operation: it replaces the incoming label with an outgoing label.

C.The egress LSR performs label imposition (push) before forwarding the IP packet to the destination.

D.PHP is enabled only when the egress LSR is not directly connected to the penultimate LSR.

E.By default, PHP is disabled on Cisco IOS routers and must be explicitly configured.

AnswersA, B

Correct. PHP offloads the label removal to the penultimate LSR, reducing egress LSR work.

Why this answer

In MPLS forwarding, label imposition (push) occurs at the ingress LSR, disposition (pop) at the egress LSR, and swapping (swap) at intermediate LSRs. The PHP (Penultimate Hop Popping) feature causes the penultimate LSR to pop the label before the egress LSR receives the packet, so the egress LSR sees only the IP packet. Option A is correct: PHP reduces the load on the egress LSR.

Option B is correct: an intermediate LSR typically swaps the top label. Option C is false: the egress LSR does not impose a label; it removes it. Option D is false: PHP is the default behavior for directly connected egress LSRs.

Option E is false: PHP is not disabled by default; it is enabled.

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MCQeasy

A network engineer runs the following command on Router R1: R1# show ip route ospf Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP a - application route + - replicated route, % - next hop override Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks O 10.1.1.0/24 [110/20] via 192.168.1.2, 00:15:30, GigabitEthernet0/0 O 10.2.2.0/24 [110/30] via 192.168.1.2, 00:15:30, GigabitEthernet0/0 Based on this output, which statement is correct?

A.The router has a default route via OSPF.

B.The router has two OSPF routes to different subnets.

C.The OSPF neighbor is down.

D.The metric for 10.2.2.0/24 is 20.

AnswerB

Two OSPF routes are listed: 10.1.1.0/24 and 10.2.2.0/24.

Why this answer

The output shows two OSPF routes via the same next hop. The administrative distance is 110 (default for OSPF), and the metrics are 20 and 30. No problems are indicated; the routes are present and valid.

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MCQmedium

What is the default hello interval for the Label Distribution Protocol (LDP) on a Cisco IOS-XE router?

A.5 seconds

B.10 seconds

C.15 seconds

D.3 seconds

AnswerA

The default LDP hello interval is 5 seconds.

Why this answer

LDP hello messages are sent every 5 seconds by default on Cisco IOS-XE routers to discover and maintain adjacencies.

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MCQhard

A network engineer is troubleshooting MPLS TE where a tunnel is configured with explicit path but the tunnel remains down. The show mpls traffic-eng tunnels command shows 'Path computation failed' and the show mpls traffic-eng topology command shows that the explicit path includes a router that is not in the TED. What is the most likely cause?

A.The router in the explicit path does not have MPLS TE enabled.

B.The explicit path is configured with a loose next-hop.

C.The tunnel destination is not reachable via the IGP.

D.The mpls traffic-eng tunnels command is missing on the headend.

AnswerA

Correct because for a router to appear in the TED, MPLS TE must be enabled globally and on its interfaces; otherwise, the headend cannot include it in the path.

Why this answer

The explicit path includes a router that is not in the TED, meaning the headend cannot find that router in the traffic engineering database. This is because MPLS TE is not enabled on that router or its interfaces, so its link attributes are not advertised.

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MCQmedium

A network engineer runs the following command to verify MPLS forwarding: R1# show mpls forwarding-table 192.168.1.0 255.255.255.0 detail Output: Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or Tunnel Id Switched interface 101 201 192.168.1.0/24 0 Gi0/0 10.0.0.2 MAC/Encaps: 14/18, MTU: 1500, Label Stack {201} No output feature configured What does this output indicate?

A.Packets with label 101 will be swapped to label 201 and forwarded to 10.0.0.2

B.Packets with label 101 will be popped and forwarded as IP packets

C.The prefix 192.168.1.0/24 is directly connected

D.The label stack has two labels

AnswerA

The forwarding table shows label swap operation: incoming label 101 swapped to outgoing label 201.

Why this answer

The output shows the MPLS forwarding table entry for prefix 192.168.1.0/24. The local label is 101, outgoing label is 201, next hop is 10.0.0.2 via GigabitEthernet0/0. The label stack contains only label 201.

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MCQmedium

A network engineer runs the following command on Router R1: R1# show mpls ldp neighbor Peer LDP Ident: 10.0.0.2:0; Local LDP Ident 10.0.0.1:0 TCP connection: 10.0.0.2.646 - 10.0.0.1.52868 State: Oper; Msgs sent/rcvd: 123/120; Downstream Up time: 02:15:30 LDP discovery sources: GigabitEthernet0/0, Src IP addr: 192.168.1.2 Addresses bound to peer LDP Ident: 10.0.0.2 192.168.1.2 Based on this output, which statement is correct?

A.The LDP session is down because the state is 'Oper'.

B.The LDP session is established and operational.

C.The LDP neighbor is using upstream label distribution.

D.The LDP session is using TCP port 179.

AnswerB

'State: Oper' indicates the session is operational.

Why this answer

The output shows a single LDP neighbor with state 'Oper' (operational), indicating the LDP session is up. The 'Downstream' mode is default. The peer LDP Ident is 10.0.0.2:0, and the local LDP Ident is 10.0.0.1:0.

The addresses bound include the peer's router-id and the interface IP. No problems are indicated.

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Multi-Selecthard

Which TWO statements about MPLS label stack operations in a Layer 3 VPN (L3VPN) are true? (Choose TWO.)

Select 2 answers

A.A P router (core router) performs label swapping only on the top label in the label stack.

B.The ingress PE router imposes two labels: an outer LDP label and an inner VPN label.

C.The P router pops the inner VPN label before forwarding the packet to the egress PE.

D.The egress PE router swaps the VPN label with a new label before forwarding to the CE.

E.The P router uses the inner VPN label to make forwarding decisions.

AnswersA, B

Correct. The P router swaps the outer IGP label; it does not process the inner VPN label.

Why this answer

In MPLS L3VPN, the P router (core router) performs label swapping based on the top label (IGP label). The PE router (ingress) imposes two labels: the outer IGP label for transport and the inner VPN label for identifying the egress VRF. The P router does not look at the inner VPN label.

Option A is correct: the P router swaps only the top label. Option B is correct: the ingress PE imposes two labels. Option C is false: the P router does not pop the VPN label; it swaps the transport label.

Option D is false: the egress PE pops the VPN label, not the P router. Option E is false: the P router does not look at the VPN label; it only swaps the outer label.

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MCQmedium

Which MPLS label is used for the Router Alert function, and what is its purpose?

A.Label 1; used to alert the router to examine the packet in the control plane.

B.Label 0; used to alert the router to examine the packet.

C.Label 2; used to alert the router to examine the packet.

D.Label 3; used to alert the router to examine the packet.

AnswerA

Label 1 is the Router Alert label per RFC 3032.

Why this answer

Label 1 is the Router Alert label, used to indicate that the packet should be examined by the router's control plane, typically for OAM or RSVP-TE messages.

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MCQhard

A network engineer runs the following command to verify MPLS LDP label bindings for a specific prefix: R1# show mpls ldp bindings 10.0.0.0 255.0.0.0 Output: lib entry: 10.0.0.0/8, rev 10 local binding: label: imp-null remote binding: lsr: 10.0.0.2:0, label: imp-null remote binding: lsr: 10.0.0.3:0, label: 302 What does this output indicate?

A.R1 will pop the label for 10.0.0.0/8 before forwarding to the next hop

B.R1 will swap the label for 10.0.0.0/8

C.All neighbors are using implicit null for this prefix

D.The prefix 10.0.0.0/8 is not in the routing table

AnswerA

Implicit null (imp-null) means the router will pop the label (PHP - Penultimate Hop Popping).

Why this answer

The output shows label bindings for prefix 10.0.0.0/8. R1 has assigned implicit null label (label 3) locally, meaning it will pop the label before forwarding. Neighbor 10.0.0.2 also uses implicit null, while 10.0.0.3 uses label 302.

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Multi-Selecthard

Which THREE symptoms indicate a potential MPLS label switching issue on a Cisco router? (Choose THREE.)

Select 3 answers

A.The output of 'show mpls forwarding-table' shows 'no label' for a specific prefix.

B.The output of 'show mpls ldp neighbor' shows 'state: OPERATIONAL' for all neighbors.

C.The output of 'debug mpls ldp errors' shows 'Label bindings not received from peer'.

D.The output of 'show mpls forwarding-table' shows 'Pop tag' for a prefix on a router that is not the egress LSR.

E.The output of 'show mpls interfaces' shows 'IP' only for an interface configured for MPLS.

AnswersA, C, D

This indicates that the router has not received a label binding for that prefix from its LDP neighbor, causing packets to be forwarded without MPLS.

Why this answer

MPLS issues often manifest as incorrect label operations. 'show mpls forwarding-table' showing 'no label' for a route indicates a missing label binding. 'show mpls ldp neighbor' showing 'state: OPERATIONAL' is normal, not a symptom. 'debug mpls ldp errors' showing 'Label bindings not received' indicates a problem. 'show mpls forwarding-table' showing 'Pop tag' for a non-egress router suggests a misconfiguration. 'show mpls interfaces' showing 'IP' only (not MPLS) indicates MPLS is not enabled on the interface.

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Drag & Dropmedium

Drag and drop the steps for MPLS LDP label discovery and distribution into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

LDP begins by establishing a TCP connection between peers, then sends Hello messages to discover neighbors, forms an adjacency, exchanges label mappings, and finally populates the LIB with learned labels.

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MCQhard

An engineer configures unicast Reverse Path Forwarding (uRPF) in strict mode on an interface. After the configuration, legitimate traffic from a customer network is being dropped. The engineer confirms that the route for the customer subnet exists in the routing table and points to the correct interface. What is the most likely explanation?

A.Asymmetric routing is in use, and the return route for the source IP points to a different interface.

B.The 'allow-default' option is not enabled, so default routes are not considered.

C.The 'ip verify unicast source reachable-via any' command was used instead of 'rx'

D.The customer subnet is a summary route, and the more specific route is missing.

AnswerA

Strict uRPF requires that the best route to the source IP address points back to the same interface on which the packet was received. If asymmetric routing is present, the return path may be via a different interface, causing strict uRPF to drop the packet.

Why this answer

Strict uRPF checks that the source IP address of an incoming packet has a route in the routing table that points back to the same interface. If the customer network uses asymmetric routing (i.e., traffic comes in one interface but the return route points out a different interface), strict uRPF will drop the traffic. The edge case is that even if the route exists, if it does not point to the incoming interface, the packet is dropped.

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MCQmedium

A network engineer is troubleshooting MPLS LDP where the LDP session between two directly connected routers is not forming. The engineer runs show mpls ldp discovery and sees that LDP hellos are being sent and received on the link. However, show mpls ldp neighbor shows no neighbors. What is the most likely cause?

A.The LDP router-id is not reachable via the IGP.

B.The mpls label protocol ldp command is missing globally.

C.The interface is configured with mpls ldp igp sync.

D.The LDP session is using a non-default transport address.

AnswerA

Correct because LDP uses TCP to establish the session, and the router-id must be reachable; if the IGP does not have a route to the peer's LDP router-id, the TCP connection fails.

Why this answer

LDP hellos are exchanged, but the session does not form, indicating a problem with the transport connection. The most common cause is that the routers cannot establish a TCP connection to the LDP transport address, often due to a missing route to the LDP router-id or an ACL blocking TCP port 646.

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MCQhard

An engineer configures IPsec site-to-site VPN between two routers. The tunnel is established, but no traffic is encrypted. The engineer checks the crypto map and access-list and confirms they match the interesting traffic. What is the most likely explanation?

A.The crypto map is applied to the wrong interface, and traffic is not being matched.

B.The 'transform-set' is configured with ESP-NULL, which provides no encryption.

C.The 'crypto isakmp key' is mismatched between the two routers.

D.The 'crypto map' is not applied globally, so it does not affect traffic.

AnswerA

If the crypto map is applied to a different interface than the one carrying the interesting traffic, the traffic will not be encrypted even if the tunnel is up. The tunnel establishment only requires the crypto map to be present on the interface, but encryption only occurs for traffic matching the access-list on that specific interface.

Why this answer

A common edge case is that the crypto map is applied to the wrong interface or the access-list is not correctly referencing the traffic. However, if the tunnel is established, the issue may be that the crypto map is applied to a subinterface but the traffic is flowing through the main interface, or the 'crypto map' command is missing the 'local-address' option for multiple crypto maps. Another possibility is that the 'set peer' command is missing or the peer address is incorrect.

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MCQhard

An engineer configures MPLS on a router with OSPF as the IGP. The OSPF neighbor is stuck in EXSTART state. The engineer verifies that both routers have matching MTU values on the connecting interfaces. What is the most likely cause of this issue?

A.The OSPF network type is mismatched between the two routers.

B.The OSPF hello and dead intervals are mismatched.

C.The router ID is duplicated on one of the routers.

D.The interface is configured with 'ip ospf mtu-ignore' on one side only.

AnswerA

A mismatch in OSPF network type (e.g., broadcast vs point-to-point) can cause the neighbor to remain in EXSTART because the DD packet exchange process differs between network types, even if MTU is consistent.

Why this answer

In OSPF, a neighbor stuck in EXSTART is often due to MTU mismatch, but if MTU is confirmed matching, the issue may be a mismatch in OSPF network type (e.g., one side broadcast, the other point-to-point). This causes different behavior in the Database Description (DD) packet exchange, leading to the stuck state even with matching MTU.

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MCQmedium

What is the default LDP keepalive timer value on Cisco IOS-XE routers?

A.180 seconds

B.120 seconds

C.60 seconds

D.300 seconds

AnswerA

The default LDP keepalive timer is 180 seconds.

Why this answer

The default LDP keepalive timer is 180 seconds, which is used to maintain the LDP session if no other messages are exchanged.

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Drag & Dropmedium

Drag and drop the steps for verifying and validating MPLS operations operational state into the correct order, from first to last.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

Begin by checking the forwarding table, then review label bindings, verify LDP peer status, confirm interface-level MPLS operation, and finally validate the LSP path.

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MCQmedium

A network engineer runs the following command to debug MPLS LDP label advertisements: R1# debug mpls ldp labels Output: *Mar 1 00:01:23.456: LDP: Sent label mapping for 192.168.1.0/24, label 101 *Mar 1 00:01:23.789: LDP: Received label mapping for 192.168.2.0/24, label 201 *Mar 1 00:01:24.012: LDP: Sent label mapping for 10.0.0.0/8, label 102 *Mar 1 00:01:24.345: LDP: Received label mapping for 10.0.0.0/8, label 202 What does this output indicate?

A.LDP label bindings are being exchanged between R1 and its LDP neighbor

B.R1 is only receiving label mappings, not sending any

C.The LDP session is down

D.R1 is using implicit null label for 10.0.0.0/8

AnswerA

The output shows both sent and received label mappings, indicating successful exchange.

Why this answer

The debug output shows label mappings being exchanged between LDP peers. R1 is sending its own label bindings (e.g., label 101 for 192.168.1.0/24) and receiving label bindings from its neighbor (e.g., label 201 for 192.168.2.0/24).

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MCQhard

In MPLS, what is the default label distribution control mode for LDP on Cisco IOS-XE?

A.Ordered Label Distribution Control mode

B.Independent Label Distribution Control mode

C.Liberal Label Retention mode

D.Conservative Label Retention mode

AnswerA

Ordered mode is the default, ensuring labels are advertised only when the next hop has assigned a label.

Why this answer

The default label distribution control mode is Ordered, meaning that a router will only advertise a label for a FEC if it has a label from its next hop or if it is the egress router.

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MCQhard

A DMVPN network with EIGRP as the routing protocol experiences spoke-to-spoke tunnel failures. Hub router R1 has configuration: 'interface Tunnel0 ip nhrp network-id 1 ip nhrp map multicast dynamic ip nhrp redirect' and 'router eigrp 100 network 10.0.0.0'. Spoke router R2 shows 'show ip nhrp brief' output: '10.0.0.1/32 via 192.168.1.1, Tunnel0 created 00:10:00, dynamic' but 'show ip eigrp neighbors' shows only the hub. What is the root cause?

A.Spoke routers are missing 'ip nhrp shortcut' interface configuration, preventing dynamic spoke-to-spoke tunnel establishment.

B.EIGRP is not configured to advertise the tunnel network; need 'network 10.0.0.0' on spokes.

C.The hub router needs 'ip nhrp map multicast dynamic' to forward multicast for EIGRP; it is already present.

D.NHRP authentication mismatch between hub and spokes causes NHRP registration failure.

AnswerA

The 'ip nhrp shortcut' command on spokes enables them to install NHRP redirect routes for direct communication.

Why this answer

Spoke-to-spoke tunnels require NHRP redirect and shortcut features to trigger direct communication. The hub has 'ip nhrp redirect' but spokes must have 'ip nhrp shortcut' to install direct routes. Without this, spokes only communicate via hub, causing suboptimal routing and potential failure if hub is overloaded.

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MCQmedium

Examine this MPLS configuration on a router: ip cef ! interface GigabitEthernet0/0 ip address 172.16.1.1 255.255.255.252 mpls ip ! interface GigabitEthernet0/1 ip address 172.16.2.1 255.255.255.252 ! router eigrp 100 network 172.16.0.0 ! mpls ldp router-id Loopback0 force What is the problem with this configuration?

A.EIGRP is not supported with MPLS; OSPF or IS-IS must be used.

B.The 'mpls ldp router-id' command references Loopback0, but no loopback interface is configured, causing LDP to fail.

C.The 'mpls ip' command is missing on GigabitEthernet0/1, so MPLS will not work on that interface.

D.CEF must be enabled under each interface, not just globally.

AnswerB

If the specified router-id interface does not exist, LDP cannot determine its router ID and will not operate. A loopback must be created.

Why this answer

The LDP router-id is set to Loopback0, but Loopback0 is not configured. This will cause LDP to fail to establish a router ID, and LDP sessions will not form. Additionally, EIGRP is used but that is fine.

The missing loopback interface is the key issue.

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MCQmedium

Consider the following MPLS configuration on a Cisco router: ip cef ! interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.252 mpls ip ! interface GigabitEthernet0/1 ip address 192.168.2.1 255.255.255.252 mpls ip ! mpls ldp router-id GigabitEthernet0/0 What is the likely problem with this configuration?

A.The router-id command is incorrectly referencing a physical interface; LDP may flap if GigabitEthernet0/0 goes down.

B.Missing 'mpls label protocol ldp' under the interfaces will prevent LDP from running.

C.Cisco Express Forwarding (CEF) must be explicitly enabled globally; it is not enabled by default.

D.The configuration is correct and will work without any issues.

AnswerA

Using a physical interface as the LDP router ID is not recommended because if that interface fails, LDP sessions will reset. A loopback interface should be used for stability.

Why this answer

The 'mpls ldp router-id' command expects a loopback interface or a stable IP address, not a physical interface name. Using a physical interface can cause LDP to flap if the interface goes down. Also, the command typically uses an interface's IP address, not the interface name directly.

The correct syntax is 'mpls ldp router-id <interface> [force]', but it is best practice to use a loopback.

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MCQmedium

A network engineer runs the following command to verify MPLS LDP label bindings: R1# show mpls ldp bindings 192.168.1.0 255.255.255.0 Output: lib entry: 192.168.1.0/24, rev 8 local binding: label: 101 remote binding: lsr: 10.0.0.2:0, label: 201 remote binding: lsr: 10.0.0.3:0, label: 301 What does this output indicate?

A.The prefix 192.168.1.0/24 has a local label of 101 and two remote labels from LDP neighbors

B.The prefix 192.168.1.0/24 is not reachable via any LDP neighbor

C.Label 101 is the only label assigned to this prefix in the network

D.The LDP session with 10.0.0.2 is down

AnswerA

The output clearly shows the local binding (label 101) and two remote bindings from different LSRs.

Why this answer

The output shows the label bindings for the prefix 192.168.1.0/24 in the Label Information Base (LIB). The local label is 101, and two remote labels (201 from 10.0.0.2, 301 from 10.0.0.3) have been received from LDP neighbors.

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MCQhard

Route summarization blocks specific routes in an MPLS network. Router R1 is a PE router that summarizes routes from a VRF into BGP. Configuration: 'router bgp 65000 address-family ipv4 vrf CUSTOMER network 10.0.0.0 255.255.252.0' and 'aggregate-address 10.0.0.0 255.255.252.0 summary-only'. A specific prefix 10.0.3.0/24 is not reachable from the MPLS core. 'show ip bgp vpnv4 vrf CUSTOMER 10.0.3.0/24' output: 'Not in table'. What is the root cause?

A.The 'summary-only' keyword suppresses more specific routes, so 10.0.3.0/24 is not advertised.

B.The VRF CUSTOMER does not have the route 10.0.3.0/24 in its routing table.

C.The aggregate-address command is missing the 'as-set' keyword, causing routing loops.

D.The network statement for 10.0.0.0/22 is missing; need to advertise the aggregate.

AnswerA

With summary-only, only the aggregate is advertised; specifics are suppressed, causing loss of reachability to 10.0.3.0/24.

Why this answer

The 'summary-only' keyword in aggregate-address suppresses all more specific routes, including 10.0.3.0/24, from being advertised. This causes the specific prefix to be missing from the BGP table, leading to unreachability if the summary route does not have a valid next-hop or if the specific route is needed for traffic engineering.

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MCQhard

In an MPLS network, OSPF network type mismatch causes routing issues. Router R1 and R2 are connected via a multi-access Ethernet link. R1 has 'interface GigabitEthernet0/0 ip ospf network point-to-point', while R2 has default OSPF network type broadcast. R1 shows 'show ip ospf neighbor' output: 'Neighbor 10.0.0.2, interface address 10.0.0.2, state FULL' but 'show ip route' does not include routes from R2. What is the root cause?

A.The OSPF network type mismatch causes R1 to ignore Type 2 LSAs from R2, preventing route installation.

B.The MTU mismatch between R1 and R2 causes OSPF database synchronization failure.

C.R1 has a distribute-list blocking routes from R2.

D.R2 is not advertising any routes; need 'network' statement.

AnswerA

Point-to-point network type does not process Type 2 (network) LSAs, so routes advertised by R2 via network LSA are ignored.

Why this answer

OSPF network type mismatch on a multi-access link can cause adjacency to form but with different DR/BDR election behavior. With point-to-point on R1, it expects no DR/BDR, while broadcast on R2 expects DR election. The adjacency forms as FULL, but R1 does not accept routes from R2 because R2's LSA may have a different link type or R1 ignores them due to mismatch in network type handling.

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MCQhard

In an MPLS LDP network, routers R1 and R2 are directly connected via GigabitEthernet0/0. R1 shows 'show mpls ldp neighbor' output: 'Peer LDP Ident: 10.0.0.2:0, Local LDP Ident: 10.0.0.1:0, TCP connection: 10.0.0.2.646 - 10.0.0.1.646, State: OPERATIONAL' but 'show mpls forwarding-table' for prefix 192.168.1.0/24 shows 'No label'. R2 has the same prefix in its routing table. What is the root cause?

A.R2 does not have MPLS enabled on the interface facing the prefix's origin; LDP only labels routes learned via MPLS-enabled interfaces.

B.R1 has an ACL blocking LDP label advertisement for prefix 192.168.1.0/24.

C.The MTU mismatch between R1 and R2 causes label distribution failure.

D.R1's MPLS forwarding table is full; no room for new labels.

AnswerA

If the prefix is learned via an interface without 'mpls ip', LDP will not assign a label, causing R1 to have no label in forwarding table.

Why this answer

LDP neighbors are operational, but label binding may fail if the IGP (e.g., OSPF) has a route to the prefix but LDP does not advertise a label for it. This can occur if the prefix is a connected route on R2 but R2's LDP is not configured to advertise labels for connected routes (e.g., 'no mpls ldp advertise-labels' or route filtering). Alternatively, R2 may have the prefix via a different interface not running MPLS.

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MCQhard

A network engineer runs the following command to debug MPLS LDP session establishment: R1# debug mpls ldp session Output: *Mar 1 00:01:23.456: LDP: Session with 10.0.0.2:0 (0x1234) is UP *Mar 1 00:01:24.567: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN *Mar 1 00:01:25.678: LDP: Session with 10.0.0.2:0 (0x1234) is UP *Mar 1 00:01:26.789: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN What does this output indicate?

A.The LDP session with 10.0.0.2 is flapping

B.The LDP session with 10.0.0.2 is stable

C.The LDP session with 10.0.0.2 is using targeted hello

D.The LDP session with 10.0.0.2 is down permanently

AnswerA

The session repeatedly transitions between UP and DOWN states, indicating flapping.

Why this answer

The debug output shows the LDP session with neighbor 10.0.0.2 is flapping (repeatedly going UP and DOWN). This indicates instability in the LDP session.

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MCQhard

What is the default maximum number of labels that can be imposed in the MPLS label stack on a Cisco IOS-XE router?

A.6 labels

B.3 labels

C.10 labels

D.Unlimited

AnswerA

The default maximum label stack depth is 6 labels.

Why this answer

The default maximum label stack depth is 6 labels on Cisco IOS-XE routers, though this can be increased with the 'mpls label range' command.

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MCQmedium

A network engineer is troubleshooting MPLS L3VPN where traffic from CE1 to CE2 is being dropped. On PE1, show mpls forwarding-table shows that the label for the BGP next-hop is 'Pop tag' (implicit null). The engineer checks the remote PE and sees that it is advertising implicit null for the BGP next-hop. What is the most likely reason for the traffic drop?

A.The remote PE does not have the CE route in its VRF.

B.The penultimate hop is not popping the label correctly.

C.The MTU on the link between P and PE2 is too small.

D.The remote PE is configured with explicit null for the BGP next-hop.

AnswerA

Correct because after label pop, the packet is forwarded as IP; if the remote PE lacks the VRF route, it drops the packet.

Why this answer

Implicit null (pop tag) means the penultimate hop pops the label and forwards the IP packet. If the traffic is dropped, the issue is likely that the remote PE does not have a route to the CE in its VRF, so it drops the IP packet after label pop.

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MCQmedium

A network engineer is troubleshooting an MPLS L3VPN where CE1 cannot reach CE2. The PE routers are running OSPF as the IGP and LDP for label distribution. On PE1, the engineer sees that the VRF route for CE2's subnet is present, but the corresponding MPLS label is missing in the LFIB. The show mpls ldp neighbor command shows LDP neighbors are up. What is the most likely cause of the missing label?

A.LDP is not enabled on the interface facing the next-hop router.

B.The VRF route is not redistributed into BGP on the remote PE.

C.MTU mismatch on the link between PE1 and P causes label imposition failure.

D.The mpls label protocol ldp command is missing under the VRF.

AnswerA

Correct because LDP must be enabled on the interface that connects to the next-hop router to assign a label for the IGP route, which is used to resolve the BGP next-hop in MPLS VPN.

Why this answer

The missing label in the LFIB despite the VRF route being present indicates that LDP is not binding a label to the BGP next-hop of the VPN route. Since the IGP route to the BGP next-hop is present but LDP has not assigned a label for it, the issue is likely that LDP is not enabled on the interface facing the next-hop router.

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MCQhard

A VRF route leaking configuration causes unexpected reachability. Router R1 has VRF RED and VRF BLUE. Configuration: 'ip vrf RED rd 100:1 route-target export 100:1 route-target import 100:2' and 'ip vrf BLUE rd 100:2 route-target export 100:2 route-target import 100:1'. Router R2 is a route reflector with 'address-family ipv4 vrf RED' and 'address-family ipv4 vrf BLUE'. A host in VRF RED can ping a host in VRF BLUE, but not vice versa. What is the root cause?

A.The route reflector lacks 'address-family ipv4 vrf' configuration for both VRFs, causing incomplete route propagation.

B.The VRF BLUE has a static route pointing to a next-hop that is not reachable from VRF RED, causing asymmetric reachability.

C.The route-target import/export values are reversed; they should be identical for both VRFs.

D.MPLS LDP is not enabled on the interfaces between routers, preventing label switching.

AnswerB

If VRF BLUE imports routes from RED but uses a static route for the return path that is not leaked, return traffic fails.

Why this answer

Route leaking via route-target import/export is asymmetric if the import and export communities are not correctly matched. In this setup, VRF RED exports 100:1 and imports 100:2, while VRF BLUE exports 100:2 and imports 100:1. This allows RED to receive routes from BLUE (import 100:2 matches export 100:2) and BLUE to receive from RED (import 100:1 matches export 100:1), so bidirectional leaking should work.

However, if the route reflector is not configured to pass VPNv4 routes correctly or if there is an issue with the 'next-hop' resolution, one direction may fail. The likely cause is that the route reflector does not have the VRF interfaces in its global routing table, causing next-hop unreachable for one VRF.

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MCQmedium

In MPLS, what is the default behavior of a Cisco IOS-XE router regarding the 'auto-summary' command for BGP routes?

A.Auto-summary is disabled by default for BGP.

B.Auto-summary is enabled by default for BGP.

C.Auto-summary is enabled by default only for directly connected routes.

D.Auto-summary is disabled by default for BGP but enabled for OSPF.

AnswerA

Cisco IOS-XE disables auto-summary by default for BGP since version 12.2(8)T.

Why this answer

By default, auto-summary is disabled in Cisco IOS-XE for BGP, meaning that BGP will not automatically summarize subnets to their classful boundaries.

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MCQhard

An engineer configures a DMVPN Phase 2 network. Spoke-to-spoke tunnels are established, but traffic between spokes is not being forwarded directly; it is still going through the hub. The engineer verifies that NHRP is working and spoke-to-spoke registrations are successful. What is the most likely explanation?

A.The hub is not sending NHRP redirect messages to the spokes.

B.The spoke routers have 'ip nhrp shortcut' disabled.

C.The hub is configured with 'no ip split-horizon' on the tunnel interface.

D.The spoke routers have mismatched IPsec transform sets.

AnswerA

In DMVPN Phase 2, the hub must send NHRP redirect messages to inform spokes of the existence of a direct path. Without these redirects, spokes do not know to send traffic directly to each other.

Why this answer

In DMVPN Phase 2, spoke-to-spoke traffic requires that the spoke routers have a route to the destination prefix via the tunnel interface with the next-hop being the remote spoke's tunnel IP. If the hub is not configured to send an NHRP redirect or if the spoke does not have a route for the remote subnet via the tunnel, traffic will continue to go through the hub. The edge case is that the hub may be using a different next-hop in its routing table, or the spoke's routing table does not have a more specific route for the remote spoke's subnet via the tunnel.

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MCQhard

In an MPLS network, Router R1 is a provider edge (PE) router that redistributes BGP routes into OSPF. The network experiences intermittent loss of reachability to a specific prefix 10.10.10.0/24. R1 configuration includes: 'router ospf 1 redistribute bgp 65000 subnets metric-type 1' and 'router bgp 65000 neighbor 10.0.0.2 route-map SET-METRIC in' with a route-map that sets metric 100. R2, a P router, shows 'show ip route 10.10.10.0' output: 'O E1 10.10.10.0/24 [110/20] via 10.0.0.1, 00:00:15' but traffic fails. What is the root cause?

A.The route-map SET-METRIC is not applied to the correct neighbor direction; it should be outbound.

B.The OSPF redistribute command lacks the 'metric' keyword to use the BGP metric; default metric 20 is used, causing inconsistency.

C.The OSPF network type mismatch on the link between R1 and R2 causes adjacency issues.

D.The BGP neighbor 10.0.0.2 is not reachable due to ACL blocking.

AnswerB

Without 'metric' in redistribute, OSPF uses default metric 20, ignoring the BGP metric set by route-map, leading to incorrect cost and potential routing loops.

Why this answer

The route-map applied to BGP inbound sets metric 100, but redistribution into OSPF uses the BGP metric as the OSPF cost. However, OSPF external route cost is calculated as metric-type 1 cost plus internal cost to the ASBR. The OSPF cost of 20 indicates the BGP metric is not being used correctly; instead, the default metric of 20 is applied because the 'metric' keyword is missing in the redistribute command, causing suboptimal path and potential blackholing due to metric mismatch.

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Multi-Selectmedium

Which TWO configuration steps are required to enable MPLS on a Cisco IOS-XE router using LDP? (Choose TWO.)

Select 2 answers

A.Configure 'mpls ip' on the desired interfaces.

B.Configure 'mpls label protocol ldp' globally.

C.Configure a routing protocol (e.g., OSPF) to provide IGP reachability between LSRs.

D.Configure 'mpls forwarding-table' to allocate labels.

E.Configure 'mpls ldp router-id' to set the LDP router ID.

AnswersA, C

This command enables MPLS label switching and LDP on the interface.

Why this answer

To enable MPLS with LDP, you must configure 'mpls ip' on the interface and also enable a routing protocol (like OSPF or IS-IS) to provide reachability. The 'mpls label protocol ldp' command is optional as LDP is the default, and 'mpls ldp router-id' is optional. 'mpls forwarding-table' is not a configuration command.

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MCQmedium

A network engineer runs the following command on Router R1: R1# show mpls l2transport vc 100 detail Local interface: Gi0/0/0 up, line protocol up Destination: 10.0.0.2, VC ID: 100, VC status: down Last error: No remote LDP session Based on this output, what is the most likely cause of the VC being down?

A.The local interface Gi0/0/0 is administratively down.

B.The remote router 10.0.0.2 is not reachable via IP.

C.The LDP session between the routers is not established.

D.The VC ID 100 is mismatched on the remote router.

AnswerC

The last error confirms 'No remote LDP session'.

Why this answer

The output explicitly states 'No remote LDP session' as the last error. This indicates that the LDP session between the two routers (10.0.0.1 and 10.0.0.2) is not established, which is required for the pseudowire to come up.

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Multi-Selecthard

An engineer is troubleshooting an MPLS LDP session that fails to establish between two directly connected routers. Which TWO commands can be used to verify LDP operation? (Choose TWO.)

Select 2 answers

A.show mpls ldp neighbor

B.show mpls ldp discovery

C.show mpls ldp bindings

D.show mpls ldp session

E.show ip route

AnswersA, B

Correct. This command displays LDP neighbors and the session state (e.g., OPERATIONAL).

Why this answer

LDP session establishment can be verified using 'show mpls ldp neighbor' to see the state of the session and 'show mpls ldp discovery' to see if LDP hello packets are being exchanged. Option A is correct: 'show mpls ldp neighbor' shows the LDP session state (e.g., OPERATIONAL). Option B is correct: 'show mpls ldp discovery' shows LDP hello adjacency details.

Option C is false: 'show mpls ldp bindings' shows label bindings, not session state. Option D is false: there is no 'show mpls ldp session' command; the correct command is 'show mpls ldp neighbor'. Option E is false: 'show ip route' does not show LDP information.

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MCQmedium

A network engineer runs the following command on Router R1: R1# show bgp ipv4 unicast summary BGP router identifier 10.0.0.1, local AS number 65001 BGP table version is 10, main routing table version 10 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 10.0.0.2 4 65002 123 120 10 0 0 02:15:30 5 10.0.0.3 4 65003 50 45 10 0 0 00:00:12 Idle (PfxRcd: 0) Based on this output, what is the problem with neighbor 10.0.0.3?

A.The neighbor 10.0.0.3 is operational and exchanging prefixes.

B.The BGP session to 10.0.0.3 is flapping.

C.The neighbor 10.0.0.3 has sent 5 prefixes.

D.The BGP table version is mismatched.

AnswerB

The state 'Idle' with a short uptime indicates the session is down and trying to re-establish.

Why this answer

The neighbor 10.0.0.3 shows 'Idle' state with no prefixes received (PfxRcd: 0). The 'Idle' state in BGP indicates that the session is not established, often due to a misconfiguration (e.g., wrong AS number, no route to neighbor, or BGP not activated). The brief uptime (00:00:12) suggests it keeps trying but fails.

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MCQhard

A network engineer is troubleshooting MPLS traffic where packets are being forwarded without a label (IP forwarding) instead of being label-switched. The engineer runs show mpls forwarding-table and sees that the FEC for the destination prefix has a valid label. However, show ip cef shows that the outgoing interface is not MPLS-enabled. What is the most likely cause?

A.The outgoing interface is missing the mpls ip command.

B.The CEF is disabled globally.

C.The mpls label protocol ldp command is missing on the interface.

D.The interface is a loopback interface.

AnswerA

Correct because mpls ip on the interface enables MPLS forwarding; without it, CEF will not impose a label and will forward the packet as IP.

Why this answer

The LFIB has a label, but CEF is not imposing it, indicating that the outgoing interface is not configured for MPLS forwarding. Even if LDP assigns a label, the interface must have mpls ip enabled for label imposition to occur.

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MCQeasy

A network engineer runs the following command on Router R1: R1# show dmvpn Legend: Attrb -> S: Static, D: Dynamic, I: Incomplete N: NATed, L: Local, X: No Socket # Ent -> Number of NHRP entries with same NBMA peer NHS Status: E => Expecting Replies, R => Responding, W => Waiting UpDn Time -> Up or Down Time for a Tunnel ========================================================================== Interface: Tunnel0, IPv4 NHRP Details Type:Hub, NHRP Peers:2, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 192.168.1.2 10.0.0.2 UP 00:15:30 D 1 192.168.1.3 10.0.0.3 UP 00:10:20 D Based on this output, what is the role of Router R1?

A.Router R1 is a DMVPN spoke.

B.Router R1 is a DMVPN hub.

C.Router R1 is a DMVPN server.

D.Router R1 is a DMVPN client.

AnswerB

The output explicitly states 'Type:Hub'.

Why this answer

The output shows 'Type:Hub', indicating that Router R1 is configured as a DMVPN hub. It has two dynamic peers (spokes) connected.

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MCQhard

BGP attribute manipulation causes unexpected path selection. Router R1 and R2 are eBGP peers. R1 receives prefix 172.16.0.0/16 from R2 with MED 50 and from another peer R3 with MED 100. R1 has configuration: 'route-map SET-MED permit 10 set metric 200' applied to neighbor R2 inbound. R1 shows 'show ip bgp 172.16.0.0' output: 'BGP routing table entry for 172.16.0.0/16, version 2, Paths: (2 available, best #2) Path #1: from R2 with MED 200, Path #2: from R3 with MED 100'. The best path is via R3, but the network expects R2 to be preferred. What is the root cause?

A.The 'bgp always-compare-med' command is missing, causing MED to be ignored for paths from different ASes.

B.The route-map SET-MED should be applied outbound on R2, not inbound.

C.R2's next-hop is unreachable via IGP, causing R1 to ignore R2's path.

D.R1 has 'bgp bestpath med missing-as-worst' configured, causing missing MED to be treated as worst.

AnswerA

Without this command, MED is only compared within same AS, so R2's lower MED (200 vs 100) is not considered, and R3's path is chosen.

Why this answer

BGP best path selection uses MED only if paths are from the same AS (if 'bgp always-compare-med' is not configured). Since R2 and R3 are different ASes, MED is not compared; instead, the next tie-breaker (e.g., IGP metric to next-hop) selects R3. The route-map sets MED on R2's routes, but it does not affect the comparison because of AS path difference.

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MCQmedium

A network engineer runs the following command on Router R1: R1# show policy-map control-plane Control Plane Service-policy input: CoPP class-map: MANAGEMENT (match-all) 5 packets, 500 bytes 5 minute offered rate 0 bps police: cir 8000 bps, bc 1500 bytes conformed 5 packets, 500 bytes; actions: transmit exceeded 0 packets, 0 bytes; actions: drop conformed 0 bps, exceed 0 bps class-map: ATTACK (match-all) 100 packets, 10000 bytes 5 minute offered rate 0 bps police: cir 8000 bps, bc 1500 bytes conformed 0 packets, 0 bytes; actions: transmit exceeded 100 packets, 10000 bytes; actions: drop conformed 0 bps, exceed 0 bps Based on this output, what is happening to traffic matching class ATTACK?

A.All traffic in class ATTACK is being transmitted.

B.All traffic in class ATTACK is being dropped.

C.Traffic in class ATTACK is being rate-limited but not dropped.

D.Traffic in class ATTACK is being marked down.

AnswerB

Exceeded 100 packets, all dropped.

Why this answer

The output shows that for class ATTACK, 100 packets were exceeded and dropped. This means the traffic rate exceeded the committed information rate (CIR) of 8000 bps, and all packets were dropped as per the exceed action.

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Multi-Selecthard

Which TWO statements about MPLS Traffic Engineering (MPLS-TE) are true? (Choose TWO.)

Select 2 answers

A.MPLS-TE uses RSVP-TE to signal label-switched paths (LSPs) and reserve bandwidth.

B.The command 'show mpls traffic-eng tunnels' displays the status of MPLS-TE tunnels.

C.MPLS-TE uses LDP to distribute labels for the TE tunnels.

D.MPLS-TE requires BGP to carry the TE attributes across the network.

E.MPLS-TE requires a full mesh of IBGP sessions between all routers.

AnswersA, B

Correct. RSVP-TE is the standard signaling protocol for MPLS-TE.

Why this answer

MPLS-TE allows explicit path selection using RSVP-TE to reserve bandwidth and set up LSPs. The 'show mpls traffic-eng tunnels' command displays tunnel status. Option A is correct: RSVP-TE is the signaling protocol used for MPLS-TE.

Option B is correct: 'show mpls traffic-eng tunnels' is a valid verification command. Option C is false: MPLS-TE does not use LDP; it uses RSVP-TE. Option D is false: MPLS-TE uses the Resource Reservation Protocol (RSVP) for signaling, not BGP.

Option E is false: MPLS-TE does not require a full mesh of IBGP sessions; it uses IGP with TE extensions.

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MCQmedium

In MPLS, what is the purpose of the TTL propagation feature?

A.It propagates the MPLS label stack to all routers in the domain.

B.It copies the IP TTL into the MPLS TTL at the ingress LER, allowing traceroute to see each hop in the MPLS path.

C.It prevents TTL from being decremented in the MPLS core for security purposes.

D.It ensures that the MPLS TTL is always equal to the IP TTL at the egress LER.

AnswerB

When enabled, the IP TTL is decremented and copied to the MPLS label, so each LSR decrements the TTL, making traceroute visible.

Why this answer

The TTL propagation feature controls how the IP TTL is handled when packets enter an MPLS domain. By default, the IP TTL is copied to the MPLS TTL (propagation), allowing traceroute to work across the MPLS network. When disabled, the MPLS TTL is set to 255, hiding the core from traceroute.

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Multi-Selectmedium

Which TWO commands would a network engineer use to verify the MPLS label forwarding table on a Cisco IOS-XE router? (Choose TWO.)

Select 2 answers

A.show mpls forwarding-table

B.show mpls ldp neighbor

C.show mpls label table

D.show ip route

E.show mpls interfaces

AnswersA, C

This command displays the MPLS forwarding table, including incoming labels, outgoing labels, and next-hop information.

Why this answer

The MPLS label forwarding table is verified using 'show mpls forwarding-table' and 'show mpls label table'. The former displays outgoing labels for prefixes, while the latter shows local label bindings. Other commands either show LDP neighbors or are invalid.

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