300-410 Layer 3 Technologies Practice Question
A network engineer is troubleshooting an MPLS Layer 3 VPN on Cisco IOS XE routers. A customer edge (CE) router is not receiving routes from the provider edge (PE) router. The engineer suspects a VRF configuration issue. Which two commands should the engineer use to verify the VRF routing table and the BGP VPNv4 address family? (Choose two.)
⚠ Common exam trap
The trap here is focusing on MPLS LDP or global BGP commands, which do not show VRF-specific or VPNv4 routing information needed for this issue.
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
✓
show bgp vpnv4 unicast all
To troubleshoot MPLS L3VPN route propagation, the engineer must check both the VRF routing table and the BGP VPNv4 table. The `show ip route vrf CUSTOMER` command reveals whether routes are installed in the VRF, while `show bgp vpnv4 unicast all` shows the VPNv4 routes exchanged between PEs. Together, they help isolate whether the issue is with VRF configuration, route targets, or BGP VPNv4 peering.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
show vrf detail
Why it's wrong here
The `show vrf detail` command displays the configuration and status of VRFs, including interfaces assigned, route distinguisher, and route targets. While it is useful to verify VRF parameters, it does not show the actual routing table or BGP VPNv4 routes. In this scenario, the engineer needs to see if routes are present in the VRF and VPNv4 table, so this command alone is insufficient.
- ✗
show ip bgp summary
Why it's wrong here
The `show ip bgp summary` command displays the status of BGP neighbors in the global routing table, not per-VRF or VPNv4. It shows whether BGP sessions are established and the number of prefixes received. However, for MPLS L3VPN, the relevant BGP session is the VPNv4 session between PEs, and VRF-specific information is not shown here. It is useful for general BGP health but not for VRF-specific troubleshooting.
- ✓
show bgp vpnv4 unicast all
Why this is correct
The `show bgp vpnv4 unicast all` command displays the BGP VPNv4 table, which contains routes from all VRFs. It shows the VPNv4 prefixes, their attributes, and the associated route distinguishers and route targets. This is critical to verify that the PE is receiving and advertising VPNv4 routes correctly. If routes are missing here, the issue may be with BGP configuration or route targets.
- ✓
show ip route vrf CUSTOMER
Why this is correct
The `show ip route vrf CUSTOMER` command displays the routing table for the specified VRF, showing routes learned from the CE and any redistributed routes. It helps verify whether the PE has installed routes for that VRF. If the VRF routing table is empty or missing expected routes, it indicates a problem with VRF configuration or route redistribution. This is essential for troubleshooting VRF-specific routing.
- ✗
show mpls ldp neighbor
Why it's wrong here
The `show mpls ldp neighbor` command displays the status of LDP sessions, which are used to exchange labels for MPLS forwarding. While LDP is important for MPLS connectivity, it does not directly show VRF routing or BGP VPNv4 information. In this scenario, the CE is not receiving routes, which is a Layer 3 VPN control plane issue, so LDP neighbor status is not the primary troubleshooting command.
Go deeper
Related to this question
Learn chapter
Device Management and Network Monitoring (SNMP, Syslog, NetFlow)
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
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
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