mediumMultiple Choice
300-410 Practice Question: Examine the following partial MPLS configuration…
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?
⚠ Common exam trap
300-410 often tests the misconception that LDP requires route redistribution or that 'force' is invalid, when in fact LDP only needs IGP reachability to the router ID and 'force' simply applies the router ID immediately.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
LDP will establish a session with the neighbor on GigabitEthernet0/0, using Loopback0 as the transport address.
The command 'mpls ldp router-id Loopback0 force' forces LDP to use the Loopback0 interface address as the LDP router ID, which becomes the transport address for the LDP session. Because the interface has 'mpls ip' and 'mpls label protocol ldp' enabled and OSPF advertises the connected subnet, LDP will form a session with the directly connected neighbor on GigabitEthernet0/0 using that loopback-derived transport address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
LDP will establish a session with the neighbor on GigabitEthernet0/0, using Loopback0 as the transport address.
Why this is correct
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.
- ✗
LDP will use the IP address of GigabitEthernet0/0 as the router ID because 'force' is not valid.
Why it's wrong here
The 'force' keyword is valid and instructs LDP to adopt Loopback0 as router ID immediately, even if that address is not yet the highest loopback. Without it, LDP waits for session teardown before switching. The option tempts those who misremember 'force' as unsupported syntax on IOS-XE.
- ✗
LDP sessions will fail because OSPF is not redistributed into LDP.
Why it's wrong here
LDP does not require OSPF redistribution; it discovers neighbours via UDP multicast on MPLS-enabled interfaces and builds sessions over TCP, relying only on IP reachability. Redistribution concerns routing protocol prefixes, not label distribution. This option tempts candidates who confuse LDP with BGP-based label exchange, where route redistribution into the label protocol would matter.
- ✗
MPLS forwarding will not occur because 'mpls label protocol ldp' is redundant and causes a conflict.
Why it's wrong here
Explicitly stating 'mpls label protocol ldp' is valid and matches the interface default; it configures LDP rather than conflicting with it. MPLS forwarding proceeds normally once IGP reachability and LDP adjacency exist. The option tempts candidates who assume any explicitly configured default must clash with another setting.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
VRF-Lite and Multi-Protocol BGP
Key term
MPLS Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.