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CCNA Mpls Questions

58 questions · Mpls topic · All types, answers revealed

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1
MCQmedium

interface GigabitEthernet0/1 ip address 10.1.1.1 255.255.255.0 mpls ip ! interface GigabitEthernet0/2 ip address 10.2.2.1 255.255.255.0 mpls ip ! router ospf 1 network 10.0.0.0 0.255.255.255 area 0 ! router ldp interface GigabitEthernet0/1 ! What is the effect of this configuration?

A.LDP will only form an adjacency over GigabitEthernet0/1; no label exchange occurs on GigabitEthernet0/2.
B.LDP will automatically enable on GigabitEthernet0/2 because MPLS is enabled there.
C.The configuration will fail because LDP must be enabled on all MPLS interfaces.
D.OSPF will automatically enable LDP on all interfaces in area 0.
AnswerA

Correct. LDP adjacencies are only formed on interfaces where LDP is explicitly enabled.

Why this answer

LDP is only enabled on GigabitEthernet0/1, not on GigabitEthernet0/2. This means LDP will not form an adjacency over GigabitEthernet0/2, and MPLS forwarding may be incomplete.

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2
MCQeasy

A network engineer runs the following command on Router R9: R9# show mpls ldp bindings 10.9.9.0 255.255.255.0 lib entry: 10.9.9.0/24, rev 10 local binding: label: 22 remote binding: lsr: 10.9.9.1:0, label: 23 remote binding: lsr: 10.9.9.2:0, label: 24 remote binding: lsr: 10.9.9.3:0, label: 25 Based on this output, how many remote LDP peers have advertised a label for the prefix 10.9.9.0/24?

A.1
B.2
C.3
D.4
AnswerC

Three remote LSRs are listed: 10.9.9.1:0, 10.9.9.2:0, and 10.9.9.3:0.

Why this answer

The output shows three remote bindings from different LSRs (10.9.9.1, 10.9.9.2, 10.9.9.3), each with a different label. So three remote peers have advertised labels.

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3
MCQmedium

An enterprise is implementing MPLS L3VPN to connect multiple branch offices. The PE routers are using eBGP to exchange VPNv4 routes. The engineer notices that some VPN routes are not being advertised to the remote PE. The 'show bgp vpnv4 unicast all' on the local PE shows the routes as valid but not best. What is the most likely reason?

A.The route has a higher local preference than the best path.
B.The route is not valid due to a missing label.
C.The route is not in the BGP table.
D.The route has a higher MED value than the best path.
AnswerA

Correct because BGP selects the best path based on local preference; a higher local preference makes a route less preferred.

Why this answer

In BGP, only the best path is advertised to peers. If a route is valid but not best, it may be due to a higher local preference or other BGP path selection criteria. Option A is correct.

Option B is wrong because the route is valid; Option C is wrong because the route is present; Option D is wrong because MED is not typically set by default.

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4
MCQhard

A network engineer is configuring MPLS TE (Traffic Engineering) in an MPLS core to optimize bandwidth utilization. After enabling MPLS TE on all core routers and configuring tunnels, the engineer notices that traffic is not being rerouted when a link fails. The 'show mpls traffic-eng tunnels' shows the tunnels are up but not using the backup path. What is the most likely missing configuration?

A.MPLS TE FRR (Fast Reroute) is not configured on the tunnels.
B.LDP is not enabled on the core interfaces.
C.RSVP is not configured on the core routers.
D.OSPF is not configured with MPLS TE extensions.
AnswerA

Correct because FRR provides backup paths for link failures in MPLS TE.

Why this answer

MPLS TE requires explicit backup path configuration, such as FRR (Fast Reroute) or backup tunnels, to provide protection. Without it, traffic will not be rerouted automatically. Option A is correct.

Option B is wrong because LDP is not required for TE; Option C is wrong because RSVP is the signaling protocol, not the issue; Option D is wrong because link-state routing is fine.

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5
Drag & Dropmedium

Drag and drop the steps of MPLS Traffic Engineering (TE) tunnel setup (RSVP) 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

MPLS TE tunnel setup begins with IGP extension configuration to propagate link attributes, followed by explicit path definition. RSVP-TE then signals the tunnel using PATH messages, which are processed by intermediate routers to reserve bandwidth. Finally, RESV messages confirm the reservation and establish the tunnel.

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6
Drag & Dropmedium

Drag and drop the steps of MPLS VPN (L3VPN) service provisioning 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

First, the provider edge (PE) router must have IGP and LDP running in the core. Then the VRF is defined with route distinguisher and import/export RTs. The customer edge (CE) interface is placed into the VRF.

MP-BGP is configured between PEs to exchange VPNv4 routes. Finally, the CE routes are redistributed into the VRF and advertised via MP-BGP.

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7
MCQeasy

A network engineer runs the following command on Router R4: R4# show mpls interfaces Interface IP Tunnel BGP Static Operational GigabitEthernet0/0 Yes No No No Yes GigabitEthernet0/1 Yes No No No Yes GigabitEthernet0/2 No No No No No Based on this output, what can be concluded?

A.MPLS is enabled and operational on GigabitEthernet0/0 and GigabitEthernet0/1.
B.MPLS is enabled on all three interfaces, but only Gi0/0 and Gi0/1 are operational.
C.BGP and Static label switching are enabled on Gi0/0 and Gi0/1.
D.Tunnel interfaces are configured on Gi0/0 and Gi0/1.
AnswerA

Both interfaces show IP: Yes and Operational: Yes.

Why this answer

The command shows which interfaces are enabled for MPLS. The 'IP' column indicates if MPLS is enabled for IP forwarding. 'Operational' shows if MPLS is actually up. Gi0/2 has MPLS disabled (IP: No) and is not operational.

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8
MCQmedium

interface GigabitEthernet0/1 ip address 10.1.1.1 255.255.255.0 mpls ip ! interface GigabitEthernet0/2 ip address 10.2.2.1 255.255.255.0 mpls ip ! router ospf 1 network 10.0.0.0 0.255.255.255 area 0 ! router ldp interface GigabitEthernet0/1 interface GigabitEthernet0/2 ! What is the effect of this configuration?

A.LDP will form adjacencies over both interfaces and distribute labels for all routes in the routing table.
B.Only OSPF routes will receive labels; static routes are ignored by LDP.
C.LDP will only form an adjacency on GigabitEthernet0/1 because it is the first interface configured.
D.The configuration will fail because OSPF and LDP are not compatible on the same interface.
AnswerA

Correct. LDP adjacencies are formed on interfaces where LDP is enabled, and labels are distributed for all routes.

Why this answer

LDP is enabled on both interfaces, but OSPF is configured with a wildcard that includes both subnets. LDP will form adjacencies and distribute labels for all OSPF routes.

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9
Matchingmedium

Drag and drop each MPLS router role on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Forwards packets based on label lookups

Imposes and removes labels at the edge of the MPLS domain

Transits labeled packets without examining the IP header

Connects to customer edge routers and provides VPN services

Customer router that connects to the provider edge

Why these pairings

LSR performs label switching, LER is at the edge, P is a core transit router, PE provides service to CE, and CE is the customer edge.

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10
Matchingmedium

Drag and drop each MPLS VPN type on the left to its matching layer on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Layer 3 IP-based VPN using MP-BGP

Layer 2 VPN transporting Ethernet or Frame Relay

Multipoint Layer 2 VPN emulating a LAN

Point-to-point Layer 2 VPN

Multicast VPN over MPLS

Why these pairings

L3VPN operates at Layer 3 (IP), L2VPN at Layer 2 (Ethernet/Frame Relay), VPLS is a specific L2VPN, VPWS is point-to-point L2VPN, and MVPN is multicast L3VPN.

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11
Matchingmedium

Drag and drop each MPLS label operation on the left to its matching action on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Adds a new label to the top of the label stack

Removes the top label from the label stack

Replaces the top label with a new label value

Pops the label at the penultimate hop before the egress LER

Copies the IP TTL value into the MPLS TTL field

Why these pairings

Push adds a new label to the stack, pop removes the top label, swap replaces the top label with a new one, PHP pops the label before the egress LER, and TTL propagation copies the IP TTL into the label TTL field.

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12
Drag & Dropmedium

Drag and drop the steps of LDP session establishment between LSRs 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 session establishment starts with discovering neighbors via Hello messages over UDP, then opening a TCP connection. The LSRs exchange initialization parameters over TCP, followed by Keepalive messages to confirm the session. Finally, label mappings are exchanged for FECs.

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13
Multi-Selecthard

Which three statements about MPLS VPN (Layer 3 VPN) are true? (Choose three.)

Select 3 answers
A.PE routers maintain separate VRF instances for each customer.
B.Route distinguishers (RDs) are used to make overlapping customer prefixes unique.
C.Route targets (RTs) control the import and export of routes between VRFs.
D.P routers must maintain customer VPN routing information.
E.MPLS VPNs use a single label to forward packets across the service provider core.
AnswersA, B, C

Correct because VRFs isolate customer routing tables on the PE.

Why this answer

In MPLS Layer 3 VPNs, the PE routers maintain separate VRF instances for each customer. Route distinguishers (RDs) make overlapping customer prefixes unique, while route targets (RTs) control the import/export of routes between VRFs. The P (provider) routers do not need to know about customer routes; they only switch based on MPLS labels.

Option D is incorrect because P routers do not maintain customer routes. Option E is incorrect because MPLS VPNs use two labels: the inner label identifies the egress PE, and the outer label is used for transport through the core.

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14
Drag & Dropmedium

Drag and drop the steps of MPLS LDP label distribution and FIB population 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

First, IP routing must be operational so that the IGP converges. Then LDP is enabled on interfaces and forms neighbor relationships. LDP then assigns local labels to FECs and advertises them to neighbors.

The remote label is received and installed in the LIB. Finally, the LFIB is populated with the best label bindings for forwarding.

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15
MCQhard

A network engineer is troubleshooting an MPLS L2VPN (VPWS) where two customer sites are connected via a pseudowire. The engineer has configured the xconnect on both PE routers, but the customer reports that the link is down. The 'show mpls l2transport vc' command on PE1 shows the VC state as 'down'. What is the most likely cause?

A.LDP is not enabled on the core interfaces between the PEs.
B.The VC ID is different on the two PEs.
C.The VC type is not set to Ethernet.
D.The encapsulation is set to VLAN instead of Ethernet.
AnswerA

Correct because LDP is required to exchange labels for the pseudowire.

Why this answer

In MPLS L2VPN, the VC state depends on the MPLS label path. If LDP is not exchanging labels for the pseudowire, the VC will remain down. Option A is correct.

Option B is wrong because the VC ID must match; Option C is wrong because the VC type must match; Option D is wrong because the encapsulation must match.

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16
MCQmedium

interface GigabitEthernet0/1 ip address 10.1.1.1 255.255.255.0 mpls ip mpls label protocol tdp ! router ospf 1 network 10.1.1.0 0.0.0.255 area 0 ! router ldp interface GigabitEthernet0/1 ! Which statement about this configuration is true?

A.The interface will use TDP for label distribution, ignoring the LDP configuration under router ldp.
B.The router will use LDP because the global configuration overrides the interface command.
C.Both TDP and LDP will be used simultaneously on the interface.
D.The configuration will fail because TDP is not supported on this platform.
AnswerA

Correct. The interface-level 'mpls label protocol tdp' overrides the global LDP configuration, so TDP is used on that interface.

Why this answer

The interface is configured with TDP (Cisco proprietary) while the router is configured for LDP (standard). This mismatch will prevent label exchange.

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17
Matchingmedium

Drag and drop each MPLS label operation on the left to its matching action on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Adds a new label to the top of the label stack

Removes the top label from the label stack

Replaces the top label with a new label value

Removes the label before the final hop

Adds one or more labels to an unlabeled packet

Why these pairings

Push adds a new label to the stack, pop removes the top label, and swap replaces the top label with a new one.

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18
MCQeasy

An engineer is configuring MPLS L3VPN with BGP as the PE-CE protocol. The customer uses eBGP between CE and PE. The engineer notices that the CE router is not receiving any VPN routes from the PE. The 'show bgp vpnv4 unicast all' on the PE shows the routes as valid and best. What is the most likely missing configuration?

A.The 'redistribute bgp' command is missing under the VRF BGP address-family on the PE.
B.The BGP session between PE and CE is not established.
C.The route-target import is not configured on the PE.
D.The VRF is not configured on the PE.
AnswerA

Correct because without redistribution, the PE does not advertise VPN routes to the CE via eBGP.

Why this answer

In MPLS L3VPN, when using eBGP between PE and CE, the PE must redistribute BGP routes into the VRF BGP process. This is done using the 'redistribute bgp' command under the VRF address-family. Option A is correct.

Option B is wrong because the routes are already in BGP; Option C is wrong because the session is up; Option D is wrong because the VRF is configured.

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19
Drag & Dropmedium

Drag and drop the steps of MPLS L2VPN (AToM) pseudowire setup 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

AToM pseudowire setup starts with configuring the attachment circuit on both PE routers. Then a pseudowire class is defined, specifying encapsulation and control word. The VC label is signaled via LDP, and the pseudowire is bound to the attachment circuit.

Finally, the pseudowire becomes operational and forwards L2 frames.

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20
MCQmedium

A network engineer runs the following command on Router R6: R6# show mpls ldp neighbor 10.6.6.7 detail Peer LDP Ident: 10.6.6.7:0; Local LDP Ident 10.6.6.6:0 TCP connection: 10.6.6.7.646 - 10.6.6.6.179 State: Oper; Msgs sent/rcvd: 200/195; Downstream Up time: 1d04h LDP discovery sources: Targeted Hello 10.6.6.6 -> 10.6.6.7, active, passive Addresses bound to peer LDP Ident: 10.6.6.7 192.168.6.7 Hold time: 15 seconds; keepalive interval: 5 seconds Peer hold time: 15 seconds; keepalive interval: 5 seconds Based on this output, what type of LDP session is this?

A.This is a link-local LDP session because the discovery source is an interface.
B.This is a targeted LDP session established between two non-directly connected routers.
C.This is a multicast LDP session because the hold time is 15 seconds.
D.This is a BGP session because the TCP connection shows port 179.
AnswerB

Targeted hellos are used for non-directly connected peers, and the output confirms targeted discovery.

Why this answer

The output shows 'Targeted Hello' in the discovery sources, indicating this is a targeted LDP session (not link-local). The session is operational and uses targeted hellos.

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21
Drag & Dropmedium

Drag and drop the steps of MPLS Traffic Engineering (TE) tunnel setup (RSVP) 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

MPLS TE tunnel setup using RSVP begins with IGP extension (OSPF/IS-IS) to flood TE link attributes, then CSPF computes the path, RSVP Path message is sent, RSVP Resv message reserves resources, and finally the tunnel is signaled and installed in the forwarding table.

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22
Multi-Selectmedium

Which two statements about MPLS label operations are true? (Choose two.)

Select 2 answers
A.The ingress LSR imposes a label onto the packet.
B.The egress LSR removes the label before forwarding the IP packet.
C.The egress LSR pushes a new label onto the packet.
D.Each LSR in the LSP performs label imposition.
E.Transit LSRs perform label imposition.
AnswersA, B

Correct because the ingress LSR pushes the initial label onto the packet.

Why this answer

In MPLS, the ingress LSR imposes (pushes) a label onto the packet. At each intermediate LSR, the label is swapped (the incoming label is replaced with an outgoing label). The egress LSR removes (pops) the label before forwarding the IP packet.

Penultimate Hop Popping (PHP) is a feature where the penultimate router pops the label, so the egress router receives only an IP packet. Option C is incorrect because the egress LSR always pops the label, not pushes. Option D is incorrect because label imposition occurs only at the ingress, not at every LSR.

Option E is incorrect because label swapping is the action at transit LSRs, not label imposition.

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23
Drag & Dropmedium

Drag and drop the steps of PHP (Penultimate Hop Popping) operation 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

PHP operation begins with the egress LSR assigning a label to a FEC and advertising it. The penultimate hop receives this label and recognizes implicit-null. The penultimate hop then pops the label before forwarding the packet.

The egress receives an unlabeled packet and performs a standard IP lookup.

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24
MCQmedium

ip vrf BLUE rd 100:1 route-target export 100:1 route-target import 100:1 ! interface GigabitEthernet0/1 ip vrf forwarding BLUE ip address 10.1.1.1 255.255.255.0 ! router bgp 65000 neighbor 192.168.1.1 remote-as 65000 neighbor 192.168.1.1 update-source Loopback0 address-family ipv4 vrf BLUE neighbor 192.168.1.1 activate network 10.1.1.0 mask 255.255.255.0 ! What is missing from this MPLS L3VPN configuration?

A.The BGP neighbor needs 'send-community extended' under the address-family to exchange VPN routes.
B.The VRF definition is missing the 'mdt' command for multicast VPN.
C.The interface needs 'mpls ip' enabled for MPLS forwarding.
D.The BGP neighbor needs 'remote-as 65000' under the VRF address-family.
AnswerA

Correct. Without 'send-community extended', the router will not send extended communities, which are essential for VPN route import/export.

Why this answer

The configuration lacks the 'neighbor 192.168.1.1 send-community extended' command under the BGP address-family, which is required to exchange VPNv4 routes with extended communities.

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25
Multi-Selectmedium

Which two statements about MPLS label operations are true? (Choose two.)

Select 2 answers
A.The ingress LSR performs a label push operation.
B.Transit LSRs perform a label swap operation.
C.The egress LSR performs a label push operation.
D.PHP (Penultimate Hop Popping) causes the egress LSR to pop the label.
E.The egress LSR always performs an IP lookup after label removal.
AnswersA, B

Correct because the ingress LSR adds the initial MPLS label to the packet.

Why this answer

In MPLS, the ingress LSR pushes a label onto the packet, and transit LSRs swap the incoming label with an outgoing label based on the LFIB. PHP removes the label before the egress LSR, so the egress LSR does not perform a label lookup. The egress LSR forwards based on the IP header after label removal.

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26
MCQmedium

An engineer is configuring MPLS L3VPN with OSPF as the PE-CE protocol. The customer wants to ensure that routes from the MPLS backbone are not redistributed back into the customer's OSPF domain. What configuration should the engineer apply on the PE router?

A.Configure the 'domain-id' under the OSPF process in the VRF.
B.Configure a sham-link between the PE routers.
C.Use the 'capability vrf-lite' command under OSPF.
D.Apply a route-map to filter routes redistributed into OSPF.
AnswerA

Correct because the domain-id prevents routes from being redistributed back into the customer's OSPF domain.

Why this answer

In MPLS L3VPN, the 'domain-id' OSPF attribute prevents redistribution of routes from the backbone into the customer's OSPF domain. Option A is correct. Option B is wrong because 'sham-link' is for backdoor links; Option C is wrong because 'capability vrf-lite' is for VRF-lite; Option D is wrong because 'redistribute connected' is not related.

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27
Matchingmedium

Drag and drop each MPLS VPN type on the left to its matching layer on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Operates at Layer 3 using IP routing and VRF

Operates at Layer 2, emulating Ethernet or Frame Relay

Multipoint L2VPN that emulates a LAN

Point-to-point L2VPN that emulates a leased line

L2VPN control plane using BGP for MAC/VXLAN distribution

Why these pairings

L3VPN uses IP routing (Layer 3) and VRF, L2VPN emulates Layer 2 services like Ethernet, VPLS is a multipoint L2VPN, VPWS is a point-to-point L2VPN, and EVPN is a modern L2VPN control plane.

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28
MCQhard

A network engineer runs the following command on Router R2: R2# show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or Tunnel Id Switched interface 16 Pop Label 10.1.1.1/32 0 Gi0/0 192.168.1.1 17 18 10.2.2.0/24 1500 Gi0/1 192.168.2.3 18 Untagged 10.3.3.0/24 0 Gi0/2 192.168.3.4 Based on this output, what is the correct interpretation?

A.For prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'.
B.For prefix 10.2.2.0/24, the router will impose label 18 onto the packet.
C.For prefix 10.3.3.0/24, the router will forward the packet with an MPLS label of 18.
D.The router has received 1500 bytes for prefix 10.2.2.0/24, and the outgoing interface is Gi0/1.
AnswerA

Pop Label indicates PHP, so the router removes the label.

Why this answer

The forwarding table shows label operations. For prefix 10.1.1.1/32, the outgoing label is 'Pop Label' meaning PHP (Penultimate Hop Popping). For 10.2.2.0/24, label 17 is swapped to 18.

For 10.3.3.0/24, 'Untagged' means the packet is forwarded without an MPLS label (e.g., to a non-MPLS interface).

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29
Multi-Selectmedium

Which two statements about MPLS label distribution protocol (LDP) are true? (Choose two.)

Select 2 answers
A.LDP uses TCP port 646 for session establishment.
B.LDP hello messages are sent as UDP packets to multicast address 224.0.0.2.
C.LDP uses UDP for session establishment.
D.LDP uses RSVP to distribute labels.
E.LDP assigns labels only to BGP routes.
AnswersA, B

Correct because LDP sessions use TCP port 646 for reliable communication.

Why this answer

LDP uses TCP port 646 for session establishment and UDP for discovery (hello messages). LDP sessions are established between directly connected LSRs by default, but can also be established between non-adjacent LSRs using targeted hellos. LDP assigns labels to every prefix in the routing table by default.

Option C is incorrect because LDP uses TCP, not UDP, for session establishment. Option D is incorrect because LDP does not use RSVP; that is for traffic engineering. Option E is incorrect because LDP assigns labels to all prefixes, not just BGP routes.

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30
MCQmedium

An engineer is troubleshooting an MPLS VPN where CE1 (10.1.1.0/24) cannot reach CE2 (10.2.2.0/24). The PE routers are running OSPF with the CE routers. On PE1, the 'show ip route vrf CUSTOMER' output shows 10.2.2.0/24 as an OSPF route, but the prefix is not present in the global BGP table. What is the most likely cause?

A.Redistribution from OSPF into BGP under the VRF is not configured on PE1.
B.The OSPF adjacency between PE1 and CE1 is down.
C.The VRF forwarding table on PE1 is full.
D.MPLS LDP is not enabled on the PE1-CE1 link.
AnswerA

Correct because VRF routes must be redistributed into BGP to be advertised as VPNv4 prefixes.

Why this answer

In MPLS L3VPN, CE routes must be redistributed into BGP (VPNv4) on the PE. If OSPF routes are present in the VRF but not in BGP, redistribution is missing. Option A correctly identifies this.

Option B is wrong because OSPF is running; Option C is irrelevant; Option D would affect label allocation, not route advertisement.

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31
Matchingmedium

Drag and drop each MPLS role on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Forwards MPLS packets by performing label lookup and swapping

Pushes labels on ingress and pops labels on egress

Core router that swaps labels without pushing or popping

Edge router that connects customer sites and runs MPLS VPNs

Customer edge router that connects to the PE

Why these pairings

LSR forwards packets based on labels, LER pushes/pops labels at the edge, P is a core LSR that only swaps labels, PE provides VPN services at the edge, and CE is the customer device connecting to the MPLS network.

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32
MCQmedium

ip vrf RED rd 200:1 route-target export 200:1 route-target import 200:1 ! interface GigabitEthernet0/1 ip vrf forwarding RED ip address 10.1.1.1 255.255.255.0 ! router bgp 65000 neighbor 192.168.1.1 remote-as 65000 neighbor 192.168.1.1 update-source Loopback0 address-family vpnv4 neighbor 192.168.1.1 activate neighbor 192.168.1.1 send-community extended ! Which statement about this configuration is true?

A.The configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with 'address-family ipv4 vrf RED'.
B.The 'send-community extended' command is unnecessary because it is enabled by default.
C.The interface GigabitEthernet0/1 requires 'mpls ip' to forward MPLS packets.
D.The VRF RED will automatically import routes from the VPNv4 address-family without additional configuration.
AnswerA

Correct. The VRF needs to be activated under BGP to advertise and receive VPN routes.

Why this answer

The BGP configuration includes 'send-community extended' under the VPNv4 address-family, which is required for MPLS L3VPN route exchange. However, the VRF RED is defined but not used in BGP.

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33
Matchingmedium

Drag and drop each LDP message type on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Discovers LDP neighbors on a link

Establishes and negotiates LDP session parameters

Maintains an established LDP session

Advertises label bindings for FECs

Reports errors or advisory information

Why these pairings

Discovery uses Hello messages, Session uses Initialization/Keepalive, Advertisement uses Label Mapping, and Notification signals errors.

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34
Drag & Dropmedium

Drag and drop the steps of PHP (Penultimate Hop Popping) operation 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

PHP begins with egress LSR assigning implicit-null label (3) to FEC, advertising it upstream, penultimate LSR popping the label, forwarding the IP packet without label, and egress LSR performing IP lookup.

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35
MCQhard

A service provider uses MPLS L3VPN with OSPF as the PE-CE routing protocol. A customer reports that a new subnet added on CE1 is not reachable from CE2, even though the PE1 router has the route in its VRF and BGP table. The 'show ip bgp vpnv4 vrf CUSTOMER' on PE2 shows the prefix with a valid next-hop. What should the engineer check next?

A.Verify that LDP has allocated a label for the BGP next-hop address on PE2.
B.Check if OSPF is redistributed into BGP on PE1.
C.Ensure the route is present in the global BGP table on PE2.
D.Confirm that the VRF on PE2 has the correct route-target import.
AnswerA

Correct because without a label for the next-hop, the VPN route cannot be forwarded.

Why this answer

In MPLS L3VPN, even if BGP has the route, the packet forwarding requires a valid MPLS label for the next-hop. If LDP is not resolving the BGP next-hop, the route is not usable. Option A is correct.

Option B is wrong because OSPF is fine; Option C is wrong because the route is in BGP; Option D is wrong because redistribution is already working.

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36
MCQmedium

A network engineer runs the following command on Router R3: R3# show mpls ldp bindings lib entry: 10.1.1.1/32, rev 2 local binding: label: 16 remote binding: lsr: 10.1.1.2:0, label: 17 lib entry: 10.2.2.0/24, rev 4 local binding: label: 18 remote binding: lsr: 10.1.1.2:0, label: 19 lib entry: 10.3.3.0/24, rev 6 local binding: label: 20 remote binding: lsr: 10.1.1.2:0, label: 21 Based on this output, what is true?

A.For prefix 10.1.1.1/32, the local label is 16 and the remote label from LSR 10.1.1.2 is 17.
B.The router has learned label bindings from two different LDP peers.
C.The label for prefix 10.2.2.0/24 is 18 locally and 19 remotely, indicating that the remote LSR will use label 18.
D.The LIB entry for 10.3.3.0/24 has a revision number of 6, meaning it was the sixth entry added.
AnswerA

The output clearly shows local binding label 16 and remote binding label 17.

Why this answer

The output shows the LIB (Label Information Base). For each prefix, there is a local label assigned by this router and a remote label learned from LSR 10.1.1.2. The rev number indicates the revision of the entry.

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37
MCQeasy

What is the maximum hop count for EIGRP?

A.100
B.15
C.255
D.16
AnswerA

Correct. The default maximum hop count is 100, configurable up to 255.

Why this answer

EIGRP has a default maximum hop count of 100, which can be changed up to 255.

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38
Multi-Selecthard

Which three statements about MPLS traffic engineering (MPLS-TE) are true? (Choose three.)

Select 3 answers
A.MPLS-TE uses RSVP-TE to signal LSPs and reserve resources.
B.OSPF or IS-IS can be extended to carry TE link attributes.
C.MPLS-TE allows traffic to follow paths that differ from the IGP shortest path.
D.MPLS-TE relies on LDP to distribute labels for TE tunnels.
E.MPLS-TE uses BGP to compute the best path for TE LSPs.
AnswersA, B, C

Correct because RSVP-TE is the signaling protocol for MPLS-TE, enabling bandwidth reservation and explicit paths.

Why this answer

MPLS-TE uses RSVP-TE to signal explicit paths and reserve bandwidth. It can use OSPF or IS-IS extended LSAs to advertise link attributes like bandwidth and delay. MPLS-TE allows traffic to be routed away from shortest-path IGP routes.

LDP is not involved in TE; RSVP-TE handles label assignment for TE tunnels. MPLS-TE does not use BGP for path computation; it uses CSPF (Constrained Shortest Path First).

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39
MCQeasy

What is the default OSPF hello interval on an Ethernet link in Cisco IOS?

A.10 seconds
B.30 seconds
C.40 seconds
D.5 seconds
AnswerA

Correct. The default hello interval for Ethernet (broadcast) is 10 seconds.

Why this answer

OSPF hello interval defaults to 10 seconds on broadcast and point-to-point networks (e.g., Ethernet).

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40
Drag & Dropmedium

Drag and drop the steps of MPLS FRR (Fast Reroute) backup tunnel activation 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

MPLS FRR begins with pre-configuring backup tunnel, protecting the primary LSP, detecting link/node failure via BFD or interface down, switching traffic to backup tunnel, and then signaling a new LSP for restoration.

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41
MCQmedium

An engineer is designing an MPLS L3VPN service for a customer that requires overlapping IP addresses between two sites. The customer uses OSPF as the PE-CE protocol. The engineer configures VRFs on the PE routers and assigns unique route distinguishers (RDs) and route targets (RTs). However, the customer reports that routes from one site are not being installed in the other site's VRF. What is the most likely cause?

A.The route-target export on PE1 does not match the route-target import on PE2.
B.The overlapping IP addresses cause a routing loop in OSPF.
C.OSPF cannot carry overlapping prefixes in different VRFs.
D.The route distinguisher is not unique between the two sites.
AnswerA

Correct because route targets must match for routes to be imported into the remote VRF.

Why this answer

In MPLS L3VPN, route targets control the import/export of routes between VRFs. If the RTs are not configured correctly, routes will not be exchanged. Option A is correct.

Option B is wrong because overlapping addresses are handled by VRFs; Option C is wrong because OSPF can handle overlapping addresses with proper configuration; Option D is wrong because RDs only make prefixes unique, they do not control route exchange.

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42
MCQhard

A network engineer runs the following command on Router R8: R8# show mpls ldp traffic LDP Traffic Statistics: Hellos sent: 5000, Hellos received: 4998 Initialization messages sent: 2, received: 2 Keepalive messages sent: 15000, received: 14995 Label mapping messages sent: 100, received: 95 Label withdraw messages sent: 5, received: 3 Label release messages sent: 2, received: 1 Label abort messages sent: 0, received: 0 Notification messages sent: 1, received: 2 Address messages sent: 10, received: 9 Address withdraw messages sent: 1, received: 0 Based on this output, what is a likely issue?

A.The LDP session is experiencing packet loss because the number of hellos sent and received are not equal.
B.There is a problem with label distribution because label withdraw messages are significantly higher than label release messages.
C.The router has sent 100 label mapping messages but received 95, indicating that 5 mapping messages were lost.
D.The router has sent 1 notification message and received 2, indicating errors in the LDP session.
AnswerB

Label withdraw (5) vs label release (2) suggests that some labels are being withdrawn but not released, which could indicate a problem.

Why this answer

The statistics show a mismatch between sent and received messages for several types, especially label withdraw (5 sent, 3 received) and label release (2 sent, 1 received). This may indicate packet loss or a problem with the LDP session. However, the most notable discrepancy is in label mapping messages (100 sent, 95 received), suggesting some mapping messages were lost.

But the question asks for a likely issue; the high number of label withdraws relative to releases could indicate instability.

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43
Multi-Selectmedium

Which two statements about MPLS VPN (Layer 3 VPN) are true? (Choose two.)

Select 2 answers
A.PE routers maintain separate VRF tables for each VPN customer.
B.P routers must maintain a full routing table for each VPN customer.
C.MP-BGP is used to exchange VPNv4 routes between PE routers.
D.CE routers run MPLS and participate in label distribution with the PE.
E.The VPN label is used by P routers to forward traffic across the MPLS core.
AnswersA, C

Correct because VRF (Virtual Routing and Forwarding) instances isolate customer routes on the PE.

Why this answer

In MPLS Layer 3 VPNs, the PE router maintains separate VRF tables per customer and uses MP-BGP to exchange VPNv4 routes (including the route distinguisher and VPN label). The P router does not need to know customer routes; it only swaps labels. The CE router does not participate in MPLS; it runs standard IP routing with the PE.

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44
MCQhard

A network engineer runs the following command on Router R5: R5# show mpls ldp discovery Local LDP Identifier: 10.5.5.5:0 Discovery Sources: Interfaces: GigabitEthernet0/0: xmit/recv LDP Id: 10.5.5.4:0, no hello (expired) GigabitEthernet0/1: xmit/recv LDP Id: 10.5.5.6:0 Based on this output, what is the state of the LDP session with neighbor 10.5.5.4?

A.The LDP session with 10.5.5.4 is operational because the interface is in xmit/recv mode.
B.The LDP session with 10.5.5.4 is not established because no hello messages have been received from that neighbor.
C.The LDP session with 10.5.5.4 is down because the interface is not operational.
D.The LDP session with 10.5.5.4 is using targeted discovery.
AnswerB

The 'no hello (expired)' indicates that the hello timer expired without receiving a hello, so the session cannot be established.

Why this answer

The output shows LDP discovery sources. For Gi0/0, the neighbor 10.5.5.4:0 has 'no hello (expired)', meaning the hello messages have not been received recently, so the neighbor is considered down or the session is not established.

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45
Matchingmedium

Drag and drop each LDP message type on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Discovers LDP neighbors on a link

Establishes an LDP session between peers

Maintains the LDP session and detects failures

Advertises interface addresses to LDP peers

Distributes label bindings for FECs

Why these pairings

Hello discovers neighbors, Initialization sets up the session, Keepalive maintains it, Address advertises interface addresses, and Label Mapping distributes label bindings.

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46
MCQeasy

Which BGP attribute is preferred when it has the lowest value?

A.MED (Multi-Exit Discriminator)
B.Local Preference
C.Weight
D.AS Path
AnswerA

Correct. Lower MED is preferred when comparing routes from the same neighboring AS.

Why this answer

The MED (Multi-Exit Discriminator) attribute is used to influence inbound traffic to an AS, and the path with the lowest MED is preferred.

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47
Drag & Dropmedium

Drag and drop the steps of LDP session establishment between LSRs 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 session establishment starts with Hello discovery via UDP, then TCP connection setup, LDP initialization with parameters, label exchange via KeepAlive and Label Mapping, and finally session up with full label exchange.

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48
Multi-Selecthard

Which three statements about LDP (Label Distribution Protocol) are true? (Choose three.)

Select 3 answers
A.LDP uses UDP to send Hello messages for neighbor discovery.
B.LDP establishes TCP sessions between LSRs to exchange label bindings.
C.LDP assigns labels to all prefixes in the routing table by default.
D.LDP supports traffic engineering by reserving bandwidth along LSPs.
E.LDP uses OSPF to distribute label bindings across the network.
AnswersA, B, C

Correct because LDP Hellos are sent as UDP packets to the multicast address 224.0.0.2 on port 646.

Why this answer

LDP uses Hello messages (UDP on port 646) for neighbor discovery and TCP (port 646) for session establishment and label exchange. LDP assigns labels to all prefixes in the routing table by default. LDP does not support traffic engineering; RSVP-TE is used for that.

LDP does not use OSPF for label distribution; it has its own discovery and session mechanisms.

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49
Multi-Selecthard

Which three statements about MPLS forwarding are true? (Choose three.)

Select 3 answers
A.MPLS forwarding uses the Label Forwarding Information Base (LFIB) to make forwarding decisions.
B.The LFIB is populated by label distribution protocols such as LDP.
C.The LIB stores all labels learned from LDP neighbors, but the LFIB is used for actual forwarding.
D.MPLS forwarding uses the Forwarding Information Base (FIB) for label lookups.
E.MPLS forwarding uses the Routing Information Base (RIB) to determine the next hop.
AnswersA, B, C

Correct because the LFIB is the table used for MPLS label switching.

Why this answer

MPLS forwarding is based on a label lookup in the LFIB (Label Forwarding Information Base). The LFIB is populated by label distribution protocols such as LDP or RSVP-TE. The FIB (Forwarding Information Base) is used for IP forwarding, not MPLS.

The LIB (Label Information Base) stores all labels learned from neighbors, but the LFIB is used for actual forwarding decisions. Option D is incorrect because the FIB is not used for MPLS forwarding. Option E is incorrect because the RIB (Routing Information Base) is used for IP routing, not MPLS label switching.

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50
MCQmedium

interface GigabitEthernet0/1 ip address 10.1.1.1 255.255.255.0 mpls ip mpls label protocol ldp ! router ospf 1 network 10.1.1.0 0.0.0.255 area 0 ! router ldp interface GigabitEthernet0/1 ! What is the effect of this configuration?

A.MPLS forwarding is enabled on GigabitEthernet0/1, and LDP will distribute labels for all routes in the routing table.
B.Only OSPF routes are labeled; static routes are excluded from LDP label distribution.
C.The 'mpls label protocol ldp' command is redundant because LDP is the default.
D.The configuration will fail because 'router ldp' requires an LDP router-id to be set.
AnswerA

Correct. 'mpls ip' enables MPLS forwarding, and LDP with the interface configuration will distribute labels for all routes, including OSPF-learned ones.

Why this answer

The configuration enables MPLS forwarding and LDP on the interface, with OSPF providing IGP reachability. LDP will distribute labels for prefixes learned via OSPF.

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51
Drag & Dropmedium

Drag and drop the steps of MPLS FRR (Fast Reroute) backup tunnel activation 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

MPLS FRR begins with configuring the backup tunnel on the PLR. The PLR then merges the backup tunnel with the protected LSP. When a link or node failure is detected, the PLR immediately switches traffic to the backup tunnel.

After the failure is repaired, traffic reverts to the primary LSP via make-before-break.

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52
Drag & Dropmedium

Drag and drop the steps of MPLS traffic engineering (MPLS-TE) tunnel setup 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

First, IGP must be configured with TE extensions (e.g., OSPF TE) to flood link attributes. Then MPLS-TE is enabled on interfaces. The headend router computes a path using CSPF based on constraints.

The tunnel interface is configured with the destination and constraints. Finally, RSVP-TE signals the LSP and reserves bandwidth along the path.

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53
MCQhard

A service provider is migrating from a traditional IP core to an MPLS core. The engineer has configured LDP on all core routers and verified that LDP sessions are established. However, some prefixes learned via OSPF are not being assigned labels. The 'show mpls ldp bindings' command shows missing bindings for certain routes. What is the most likely cause?

A.The routes are not present in the global routing table on the router.
B.The OSPF process is not redistributed into LDP.
C.LDP is configured to only assign labels to BGP routes.
D.The 'mpls ldp autoconfig' command is missing on OSPF.
AnswerA

Correct because LDP only assigns labels to routes that are in the routing table.

Why this answer

LDP by default only assigns labels to routes in the routing table that are not BGP routes. If the routes are not in the routing table (e.g., due to summarization or filtering), LDP will not assign labels. Option A is correct.

Option B is wrong because LDP does not require IGP; Option C is wrong because LDP can assign labels to any route; Option D is wrong because LDP does not require BGP.

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54
MCQmedium

A network engineer runs the following command on Router R1: R1# show mpls ldp neighbor Peer LDP Ident: 10.1.1.2:0; Local LDP Ident 10.1.1.1:0 TCP connection: 10.1.1.2.646 - 10.1.1.1.179 State: Oper; Msgs sent/rcvd: 120/115; Downstream Up time: 02:30:15 LDP discovery sources: GigabitEthernet0/0, Src IP addr: 192.168.1.2 Addresses bound to peer LDP Ident: 10.1.1.2 192.168.1.2 10.2.2.2 Based on this output, what can be concluded?

A.The LDP session is using TCP port 646 for LDP and port 179 for BGP, and the session is operational.
B.The LDP session is down because the state is 'Oper' but the TCP connection shows port 179.
C.The LDP neighbor is using label distribution mode 'Upstream' based on the output.
D.The LDP session has been up for 2 hours and 30 minutes, and the peer has sent 115 messages.
AnswerA

State: Oper confirms the session is up, and TCP ports 646 (LDP) and 179 (BGP) are correctly identified.

Why this answer

The output shows an established LDP session (State: Oper) between LSRs 10.1.1.1 and 10.1.1.2, with TCP port 646 (LDP) and port 179 (BGP) shown. The 'Downstream' label distribution mode is indicated. The peer's addresses include loopback and interface IPs.

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55
Drag & Dropmedium

Drag and drop the steps of MPLS L2VPN (AToM) pseudowire setup 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

AToM pseudowire setup begins with configuring attachment circuit and VC ID, then LDP targeted session for pseudowire signaling, label mapping exchange, pseudowire status notification, and finally pseudowire operational with traffic flow.

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56
Matchingmedium

Drag and drop each MPLS label field on the left to its matching bit size on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

20 bits

3 bits

1 bit

8 bits

32 bits

Why these pairings

The MPLS label has 4 fields: Label (20 bits), TC (3 bits), S (1 bit), and TTL (8 bits).

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57
MCQmedium

A network engineer runs the following command on Router R7: R7# show mpls ldp capabilities LDP Capabilities: Dynamic Capability: advertised Typed Wildcard FEC: advertised MTU Signaling: advertised P2MP: not advertised MPLS OAM: advertised LDP Graceful Restart: advertised Helper mode: enabled Restart mode: enabled Reconnect time: 120 sec Recovery time: 180 sec Based on this output, which capability is NOT supported by this router?

A.LDP Graceful Restart
B.MTU Signaling
C.P2MP (Point-to-Multipoint)
D.Dynamic Capability
AnswerC

It is listed as 'not advertised'.

Why this answer

The output lists capabilities that are advertised. P2MP (Point-to-Multipoint) is explicitly listed as 'not advertised', meaning it is not supported.

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58
Matchingmedium

Drag and drop each MPLS label field on the left to its matching bit size on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

20 bits

3 bits

1 bit

8 bits

32 bits

Why these pairings

The MPLS label is 20 bits, Traffic Class (TC) is 3 bits, Bottom of Stack (S) is 1 bit, and TTL is 8 bits, totaling 32 bits per label entry.

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