Refer to the exhibit. CE1 and CE2 cannot communicate through the service provider BGP peering is established between PE1 and PE2. IS-IS is the only routing protocol running in the service provider cor

Question

Exhibit

Options

• ASwitch the IGPs running in the core from IS-IS to OSPF to support a Cisco MPLS TE tunnel from
• BConfigure BGP between CE and PE routers.
• CConfirm that IS-IS is running with metric-style narrow.
• DVerify the MPLS LSPs.

• A
  14% (4)
• B
  4% (1)
• C
  4% (1)
• D
  79% (22)

Explanation

In an MPLS L3VPN architecture, three planes must all function correctly: the IGP (IS-IS here) for PE loopback reachability, MP-BGP (VPNv4) for VPN route exchange, and MPLS LSPs for forwarding VPN-labeled packets across the core. The problem states BGP peering is established between PE1 and PE2, and IS-IS is running - the control plane appears healthy. The missing piece is likely the MPLS forwarding plane: if LSPs are not properly established (e.g., LDP or RSVP-TE sessions are down, labels are not exchanged), packets from CE1 cannot be label-switched to CE2 even though routes exist in BGP. Answer A is wrong because IS-IS supports MPLS TE natively. Answer B may be relevant but the question implies CE-PE connectivity exists (BGP between PEs is established, implying PE has CE routes). Answer C (narrow metric-style) is unrelated to the forwarding failure described. Verifying MPLS LSPs (Answer D) directly addresses the forwarding-plane gap between a working control plane and broken data-plane connectivity.

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