MPLS practice questions

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?

Trap 1: The OSPF adjacency between PE1 and CE1 is down.

Incorrect because the route is present in the VRF, indicating the adjacency is up.

Trap 2: The VRF forwarding table on PE1 is full.

Incorrect because a full VRF table would not prevent a specific route from being in BGP.

Trap 3: MPLS LDP is not enabled on the PE1-CE1 link.

Incorrect because LDP is used for label distribution in the core, not for VPN route exchange.

A
Redistribution from OSPF into BGP under the VRF is not configured on PE1.
Correct because VRF routes must be redistributed into BGP to be advertised as VPNv4 prefixes.
B
The OSPF adjacency between PE1 and CE1 is down.
Why wrong: Incorrect because the route is present in the VRF, indicating the adjacency is up.
C
The VRF forwarding table on PE1 is full.
Why wrong: Incorrect because a full VRF table would not prevent a specific route from being in BGP.
D
MPLS LDP is not enabled on the PE1-CE1 link.
Why wrong: Incorrect because LDP is used for label distribution in the core, not for VPN route exchange.

Question 2hardmultiple choice

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?

Trap 1: Check if OSPF is redistributed into BGP on PE1.

Incorrect because the route is already in BGP, so redistribution is working.

Trap 2: Ensure the route is present in the global BGP table on PE2.

Incorrect because the route is in the VPNv4 BGP table, which is sufficient.

Trap 3: Confirm that the VRF on PE2 has the correct route-target import.

Incorrect because the route is already in the VRF BGP table, so import is working.

A
Verify that LDP has allocated a label for the BGP next-hop address on PE2.
Correct because without a label for the next-hop, the VPN route cannot be forwarded.
B
Check if OSPF is redistributed into BGP on PE1.
Why wrong: Incorrect because the route is already in BGP, so redistribution is working.
C
Ensure the route is present in the global BGP table on PE2.
Why wrong: Incorrect because the route is in the VPNv4 BGP table, which is sufficient.
D
Confirm that the VRF on PE2 has the correct route-target import.
Why wrong: Incorrect because the route is already in the VRF BGP table, so import is working.

Question 3mediummultiple choice

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?

Trap 1: The overlapping IP addresses cause a routing loop in OSPF.

Incorrect because VRFs keep the routing tables separate, preventing loops.

Trap 2: OSPF cannot carry overlapping prefixes in different VRFs.

Incorrect because OSPF can run in multiple VRFs without issue.

Trap 3: The route distinguisher is not unique between the two sites.

Incorrect because RDs only need to be unique per VRF, not across sites.

A
The route-target export on PE1 does not match the route-target import on PE2.
Correct because route targets must match for routes to be imported into the remote VRF.
B
The overlapping IP addresses cause a routing loop in OSPF.
Why wrong: Incorrect because VRFs keep the routing tables separate, preventing loops.
C
OSPF cannot carry overlapping prefixes in different VRFs.
Why wrong: Incorrect because OSPF can run in multiple VRFs without issue.
D
The route distinguisher is not unique between the two sites.
Why wrong: Incorrect because RDs only need to be unique per VRF, not across sites.

Question 4hardmultiple choice

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?

Trap 1: LDP is not enabled on the core interfaces.

Incorrect because LDP is not used for TE tunnel protection.

Trap 2: RSVP is not configured on the core routers.

Incorrect because RSVP is needed for TE signaling, but its presence alone does not provide backup paths.

Trap 3: OSPF is not configured with MPLS TE extensions.

Incorrect because TE extensions are needed for path computation, not for backup path activation.

A
MPLS TE FRR (Fast Reroute) is not configured on the tunnels.
Correct because FRR provides backup paths for link failures in MPLS TE.
B
LDP is not enabled on the core interfaces.
Why wrong: Incorrect because LDP is not used for TE tunnel protection.
C
RSVP is not configured on the core routers.
Why wrong: Incorrect because RSVP is needed for TE signaling, but its presence alone does not provide backup paths.
D
OSPF is not configured with MPLS TE extensions.
Why wrong: Incorrect because TE extensions are needed for path computation, not for backup path activation.

Open the full BGP breakdown →

Question 5mediummultiple choice

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?

Trap 1: The route is not valid due to a missing label.

Incorrect because the route is listed as valid.

Trap 2: The route is not in the BGP table.

Incorrect because the route is present.

Trap 3: The route has a higher MED value than the best path.

Incorrect because MED is only compared for routes from the same AS.

A
The route has a higher local preference than the best path.
Correct because BGP selects the best path based on local preference; a higher local preference makes a route less preferred.
B
The route is not valid due to a missing label.
Why wrong: Incorrect because the route is listed as valid.
C
The route is not in the BGP table.
Why wrong: Incorrect because the route is present.
D
The route has a higher MED value than the best path.
Why wrong: Incorrect because MED is only compared for routes from the same AS.

Question 6hardmultiple choice

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?

Trap 1: The VC ID is different on the two PEs.

Incorrect because the VC ID must match, but the question states it is configured, so this is not the issue.

Trap 2: The VC type is not set to Ethernet.

Incorrect because the VC type must match, but it is likely configured correctly.

Trap 3: The encapsulation is set to VLAN instead of Ethernet.

Incorrect because the encapsulation must match, but it is likely configured correctly.

A
LDP is not enabled on the core interfaces between the PEs.
Correct because LDP is required to exchange labels for the pseudowire.
B
The VC ID is different on the two PEs.
Why wrong: Incorrect because the VC ID must match, but the question states it is configured, so this is not the issue.
C
The VC type is not set to Ethernet.
Why wrong: Incorrect because the VC type must match, but it is likely configured correctly.
D
The encapsulation is set to VLAN instead of Ethernet.
Why wrong: Incorrect because the encapsulation must match, but it is likely configured correctly.

Question 7mediummultiple choice

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?

Trap 1: Configure a sham-link between the PE routers.

Incorrect because sham-links are used for backdoor links, not to prevent redistribution.

Trap 2: Use the 'capability vrf-lite' command under OSPF.

Incorrect because vrf-lite is used for non-MPLS environments.

Trap 3: Apply a route-map to filter routes redistributed into OSPF.

Incorrect because route-maps can filter, but the domain-id is the standard method.

A
Configure the 'domain-id' under the OSPF process in the VRF.
Correct because the domain-id prevents routes from being redistributed back into the customer's OSPF domain.
B
Configure a sham-link between the PE routers.
Why wrong: Incorrect because sham-links are used for backdoor links, not to prevent redistribution.
C
Use the 'capability vrf-lite' command under OSPF.
Why wrong: Incorrect because vrf-lite is used for non-MPLS environments.
D
Apply a route-map to filter routes redistributed into OSPF.
Why wrong: Incorrect because route-maps can filter, but the domain-id is the standard method.

Question 8hardmultiple choice

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?

Trap 1: The OSPF process is not redistributed into LDP.

Incorrect because LDP does not require redistribution; it uses the routing table directly.

Trap 2: LDP is configured to only assign labels to BGP routes.

Incorrect because LDP typically assigns labels to IGP routes as well.

Trap 3: The 'mpls ldp autoconfig' command is missing on OSPF.

Incorrect because autoconfig is used to enable LDP on interfaces, not to assign labels to routes.

A
The routes are not present in the global routing table on the router.
Correct because LDP only assigns labels to routes that are in the routing table.
B
The OSPF process is not redistributed into LDP.
Why wrong: Incorrect because LDP does not require redistribution; it uses the routing table directly.
C
LDP is configured to only assign labels to BGP routes.
Why wrong: Incorrect because LDP typically assigns labels to IGP routes as well.
D
The 'mpls ldp autoconfig' command is missing on OSPF.
Why wrong: Incorrect because autoconfig is used to enable LDP on interfaces, not to assign labels to routes.

Open the full BGP breakdown →

Question 9easymultiple choice

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?

Trap 1: The BGP session between PE and CE is not established.

Incorrect because the routes are in the VRF BGP table, indicating the session is up.

Trap 2: The route-target import is not configured on the PE.

Incorrect because the routes are already in the VRF BGP table, so import is working.

Trap 3: The VRF is not configured on the PE.

Incorrect because the VRF must be configured for the routes to be present.

A
The 'redistribute bgp' command is missing under the VRF BGP address-family on the PE.
Correct because without redistribution, the PE does not advertise VPN routes to the CE via eBGP.
B
The BGP session between PE and CE is not established.
Why wrong: Incorrect because the routes are in the VRF BGP table, indicating the session is up.
C
The route-target import is not configured on the PE.
Why wrong: Incorrect because the routes are already in the VRF BGP table, so import is working.
D
The VRF is not configured on the PE.
Why wrong: Incorrect because the VRF must be configured for the routes to be present.

Question 10mediummultiple choice

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?

Trap 1: The LDP session is down because the state is 'Oper' but the TCP…

State: Oper means operational; port 179 is the BGP port, but here it's shown as the local port for LDP (which is incorrect in real life, but the question tests reading the output as given).

Trap 2: The LDP neighbor is using label distribution mode 'Upstream' based…

The output explicitly says 'Downstream', not 'Upstream'.

Trap 3: The LDP session has been up for 2 hours and 30 minutes, and the…

The uptime is correct, but the peer has sent 115 messages (Msgs sent/rcvd: 120/115 means local sent 120, received 115).

A
The LDP session is using TCP port 646 for LDP and port 179 for BGP, and the session is operational.
State: Oper confirms the session is up, and TCP ports 646 (LDP) and 179 (BGP) are correctly identified.
B
The LDP session is down because the state is 'Oper' but the TCP connection shows port 179.
Why wrong: State: Oper means operational; port 179 is the BGP port, but here it's shown as the local port for LDP (which is incorrect in real life, but the question tests reading the output as given).
C
The LDP neighbor is using label distribution mode 'Upstream' based on the output.
Why wrong: The output explicitly says 'Downstream', not 'Upstream'.
D
The LDP session has been up for 2 hours and 30 minutes, and the peer has sent 115 messages.
Why wrong: The uptime is correct, but the peer has sent 115 messages (Msgs sent/rcvd: 120/115 means local sent 120, received 115).

Question 11hardmultiple choice

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?

Trap 1: For prefix 10.2.2.0/24, the router will impose label 18 onto the…

The outgoing label is 18, meaning it swaps the incoming label 17 to 18, not imposes a new label.

Trap 2: For prefix 10.3.3.0/24, the router will forward the packet with an…

The output says 'Untagged', meaning no label is used.

Trap 3: The router has received 1500 bytes for prefix 10.2.2.0/24, and the…

Bytes Label Switched is 1500, meaning 1500 bytes have been switched with that label, not received.

A
For prefix 10.1.1.1/32, the router will pop the MPLS label before forwarding because the outgoing label is 'Pop Label'.
Pop Label indicates PHP, so the router removes the label.
B
For prefix 10.2.2.0/24, the router will impose label 18 onto the packet.
Why wrong: The outgoing label is 18, meaning it swaps the incoming label 17 to 18, not imposes a new label.
C
For prefix 10.3.3.0/24, the router will forward the packet with an MPLS label of 18.
Why wrong: The output says 'Untagged', meaning no label is used.
D
The router has received 1500 bytes for prefix 10.2.2.0/24, and the outgoing interface is Gi0/1.
Why wrong: Bytes Label Switched is 1500, meaning 1500 bytes have been switched with that label, not received.

Question 12mediummultiple choice

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?

Trap 1: The router has learned label bindings from two different LDP peers.

All remote bindings are from the same LSR: 10.1.1.2:0.

Trap 2: The label for prefix 10.2.2.0/24 is 18 locally and 19 remotely,…

The remote label is 19, not 18. The local label is 18.

Trap 3: The LIB entry for 10.3.3.0/24 has a revision number of 6, meaning…

The rev number is per entry, not a global counter; it indicates the revision of that specific entry.

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.
The output clearly shows local binding label 16 and remote binding label 17.
B
The router has learned label bindings from two different LDP peers.
Why wrong: All remote bindings are from the same LSR: 10.1.1.2:0.
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.
Why wrong: The remote label is 19, not 18. The local label is 18.
D
The LIB entry for 10.3.3.0/24 has a revision number of 6, meaning it was the sixth entry added.
Why wrong: The rev number is per entry, not a global counter; it indicates the revision of that specific entry.

Open the full BGP breakdown →

Question 13easymultiple choice

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?

Trap 1: MPLS is enabled on all three interfaces, but only Gi0/0 and Gi0/1…

Gi0/2 has IP: No, meaning MPLS is not enabled on that interface.

Trap 2: BGP and Static label switching are enabled on Gi0/0 and Gi0/1.

The BGP and Static columns show 'No' for both interfaces.

Trap 3: Tunnel interfaces are configured on Gi0/0 and Gi0/1.

The Tunnel column shows 'No' for both.

A
MPLS is enabled and operational on GigabitEthernet0/0 and GigabitEthernet0/1.
Both interfaces show IP: Yes and Operational: Yes.
B
MPLS is enabled on all three interfaces, but only Gi0/0 and Gi0/1 are operational.
Why wrong: Gi0/2 has IP: No, meaning MPLS is not enabled on that interface.
C
BGP and Static label switching are enabled on Gi0/0 and Gi0/1.
Why wrong: The BGP and Static columns show 'No' for both interfaces.
D
Tunnel interfaces are configured on Gi0/0 and Gi0/1.
Why wrong: The Tunnel column shows 'No' for both.

Question 14hardmultiple choice

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?

Trap 1: The LDP session with 10.5.5.4 is operational because the interface…

The 'xmit/recv' indicates the interface is sending and receiving hellos, but the neighbor state shows 'no hello (expired)', meaning no hello received from that neighbor.

Trap 2: The LDP session with 10.5.5.4 is down because the interface is not…

The interface is in xmit/recv mode, meaning it is operational for sending/receiving hellos, but the neighbor is not responding.

Trap 3: The LDP session with 10.5.5.4 is using targeted discovery.

The discovery is interface-based (GigabitEthernet0/0), not targeted.

A
The LDP session with 10.5.5.4 is operational because the interface is in xmit/recv mode.
Why wrong: The 'xmit/recv' indicates the interface is sending and receiving hellos, but the neighbor state shows 'no hello (expired)', meaning no hello received from that neighbor.
B
The LDP session with 10.5.5.4 is not established because no hello messages have been received from that neighbor.
The 'no hello (expired)' indicates that the hello timer expired without receiving a hello, so the session cannot be established.
C
The LDP session with 10.5.5.4 is down because the interface is not operational.
Why wrong: The interface is in xmit/recv mode, meaning it is operational for sending/receiving hellos, but the neighbor is not responding.
D
The LDP session with 10.5.5.4 is using targeted discovery.
Why wrong: The discovery is interface-based (GigabitEthernet0/0), not targeted.

Question 15mediummultiple choice

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?

Trap 1: This is a link-local LDP session because the discovery source is an…

The discovery source is explicitly 'Targeted Hello', not an interface.

Trap 2: This is a multicast LDP session because the hold time is 15 seconds.

Hold time is a parameter for LDP sessions, not an indicator of multicast.

Trap 3: This is a BGP session because the TCP connection shows port 179.

Port 179 is the BGP port, but here it's shown as the local port for LDP (which is unusual but given in output). The session is LDP.

A
This is a link-local LDP session because the discovery source is an interface.
Why wrong: The discovery source is explicitly 'Targeted Hello', not an interface.
B
This is a targeted LDP session established between two non-directly connected routers.
Targeted hellos are used for non-directly connected peers, and the output confirms targeted discovery.
C
This is a multicast LDP session because the hold time is 15 seconds.
Why wrong: Hold time is a parameter for LDP sessions, not an indicator of multicast.
D
This is a BGP session because the TCP connection shows port 179.
Why wrong: Port 179 is the BGP port, but here it's shown as the local port for LDP (which is unusual but given in output). The session is LDP.

Question 16mediummultiple choice

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?

Trap 1: LDP Graceful Restart

It is advertised, as shown.

Trap 2: MTU Signaling

It is advertised.

Trap 3: Dynamic Capability

It is advertised.

A
LDP Graceful Restart
Why wrong: It is advertised, as shown.
B
MTU Signaling
Why wrong: It is advertised.
C
P2MP (Point-to-Multipoint)
It is listed as 'not advertised'.
D
Dynamic Capability
Why wrong: It is advertised.

Question 17hardmultiple choice

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?

Trap 1: The LDP session is experiencing packet loss because the number of…

Hellos sent 5000, received 4998; a small difference is normal due to timing.

Trap 2: The router has sent 100 label mapping messages but received 95,…

While true, this is a small difference and not necessarily a significant issue compared to the withdraw/release mismatch.

Trap 3: The router has sent 1 notification message and received 2,…

Notifications are normal for error reporting; a small number is not indicative of a major issue.

A
The LDP session is experiencing packet loss because the number of hellos sent and received are not equal.
Why wrong: Hellos sent 5000, received 4998; a small difference is normal due to timing.
B
There is a problem with label distribution because label withdraw messages are significantly higher than label release messages.
Label withdraw (5) vs label release (2) suggests that some labels are being withdrawn but not released, which could indicate a problem.
C
The router has sent 100 label mapping messages but received 95, indicating that 5 mapping messages were lost.
Why wrong: While true, this is a small difference and not necessarily a significant issue compared to the withdraw/release mismatch.
D
The router has sent 1 notification message and received 2, indicating errors in the LDP session.
Why wrong: Notifications are normal for error reporting; a small number is not indicative of a major issue.

Question 18easymultiple choice

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?

Trap 1: 1

There are three remote bindings.

Trap 2: 2

There are three remote bindings.

Trap 3: 4

There is one local binding and three remote, so total four entries but only three remote peers.

A
1
Why wrong: There are three remote bindings.
B
2
Why wrong: There are three remote bindings.
C
3
Three remote LSRs are listed: 10.9.9.1:0, 10.9.9.2:0, and 10.9.9.3:0.
D
4
Why wrong: There is one local binding and three remote, so total four entries but only three remote peers.

Question 19mediummultiple choice

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?

Trap 1: Only OSPF routes are labeled; static routes are excluded from LDP…

Incorrect. By default, LDP distributes labels for all routes in the routing table, not just OSPF routes.

Trap 2: The 'mpls label protocol ldp' command is redundant because LDP is…

Incorrect. While LDP is often the default, this command explicitly sets the label protocol to LDP, which is not redundant in all IOS versions.

Trap 3: The configuration will fail because 'router ldp' requires an LDP…

Incorrect. LDP can use the highest loopback IP as router-id automatically; no explicit configuration is required.

A
MPLS forwarding is enabled on GigabitEthernet0/1, and LDP will distribute labels for all routes in the routing table.
Correct. 'mpls ip' enables MPLS forwarding, and LDP with the interface configuration will distribute labels for all routes, including OSPF-learned ones.
B
Only OSPF routes are labeled; static routes are excluded from LDP label distribution.
Why wrong: Incorrect. By default, LDP distributes labels for all routes in the routing table, not just OSPF routes.
C
The 'mpls label protocol ldp' command is redundant because LDP is the default.
Why wrong: Incorrect. While LDP is often the default, this command explicitly sets the label protocol to LDP, which is not redundant in all IOS versions.
D
The configuration will fail because 'router ldp' requires an LDP router-id to be set.
Why wrong: Incorrect. LDP can use the highest loopback IP as router-id automatically; no explicit configuration is required.

Question 20mediummultiple choice

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?

Trap 1: The router will use LDP because the global configuration overrides…

Incorrect. Interface-level commands take precedence over global configuration.

Trap 2: Both TDP and LDP will be used simultaneously on the interface.

Incorrect. Only one label protocol can be active per interface.

Trap 3: The configuration will fail because TDP is not supported on this…

Incorrect. TDP is supported on many Cisco platforms, though it is deprecated.

A
The interface will use TDP for label distribution, ignoring the LDP configuration under router ldp.
Correct. The interface-level 'mpls label protocol tdp' overrides the global LDP configuration, so TDP is used on that interface.
B
The router will use LDP because the global configuration overrides the interface command.
Why wrong: Incorrect. Interface-level commands take precedence over global configuration.
C
Both TDP and LDP will be used simultaneously on the interface.
Why wrong: Incorrect. Only one label protocol can be active per interface.
D
The configuration will fail because TDP is not supported on this platform.
Why wrong: Incorrect. TDP is supported on many Cisco platforms, though it is deprecated.