hardMultiple Choice
350-401 Practice Question: Runs the following command on Router R1: R1# show…
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 - 10.0.0.1.179 State: Oper; Msgs sent/rcvd: 100/95; Downstream Up time: 00:10:00 LDP discovery sources: GigabitEthernet0/0, Src IP: 10.0.0.2 Addresses bound to peer LDP Ident:
10.0.0.2 192.168.2.2
Peer LDP Ident: 10.0.0.3:0, Local LDP Ident: 10.0.0.1:0 TCP connection: 10.0.0.3.646 - 10.0.0.1.179 State: Oper; Msgs sent/rcvd: 200/190; Downstream Up time: 00:20:00 LDP discovery sources: GigabitEthernet0/1, Src IP: 10.0.0.3 Addresses bound to peer LDP Ident:
10.0.0.3 192.168.3.3
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the distinction between 'Downstream' and 'Downstream-on-Demand' label advertisement modes, and candidates may mistakenly assume 'Downstream' implies on-demand behavior or overlook the explicit 'State: Oper' field indicating session health.
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
✓
The router has two LDP peers that are both operational
The output shows two LDP peers (10.0.0.2 and 10.0.0.3) with the State: Oper for both, indicating both Label Distribution Protocol sessions are fully operational. The 'Downstream' label mode confirms unsolicited downstream label advertisement, which is the default behavior. Therefore, option A is correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The router has two LDP peers that are both operational
Why this is correct
The output displays two LDP peers with IP addresses 10.0.0.2 and 10.0.0.3. Each peer entry shows 'State: Oper', meaning the LDP sessions are operational and exchanging label bindings. Therefore, the router has two active LDP neighbors, making this statement correct.
- ✗
The router is using LDP in downstream-on-demand mode
Why it's wrong here
The output indicates 'Downstream' mode, which refers to Downstream Unsolicited (DU) label advertisement, not Downstream-on-Demand (DoD). In DU mode, a router sends label bindings to its peers without waiting for a request, whereas DoD requires an explicit Label Request message. Since the mode shown is 'Downstream', the statement about DoD is incorrect.
- ✗
The LDP session with 10.0.0.2 is down
Why it's wrong here
The peer 10.0.0.2 is listed with 'State: Oper', which is short for operational. This indicates the LDP session is fully established and active, able to exchange label mapping messages. Therefore, the claim that this session is down is false.
- ✗
The router has only one LDP neighbor
Why it's wrong here
The output clearly lists two neighbors: 10.0.0.2 and 10.0.0.3, both in the operational state. A router with a single LDP neighbor would show only one peer entry in the 'show mpls ldp neighbor' output. Since there are two distinct peer entries, the 'only one neighbor' statement is incorrect.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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