Refer to the exhibit. An engineer is troubleshooting an issue where Cisco switch Switch_A fails to establish OTV connectivity to Cisco switch Switch_C. What is the cause of the issue?

Question

Exhibits

Options

• AThe broadcast group must be 232.1.1.0.
• BThe join interface must be g1/0.
• CThe control group must be 232.1.1.0.
• DThe join interface must be e1/1.

• A
  16% (9)
• B
  70% (39)
• C
  5% (3)
• D
  9% (5)

Explanation

In Cisco Overlay Transport Virtualization (OTV), the join interface is the Layer 3 interface that connects the edge device to the transport network (the routed core / WAN) where multicast groups (control, data, broadcast) are reachable. From the topology: Interface g1/0 on Switch_A is connected to the routed 20.20.20.0/30 link toward Switch_C (the transport / WAN). Interface g1/1 is a trunk toward Switch_B and carries extended VLANs (101, 111), so it belongs to the internal site-facing side, not the transport. In the show otv output, the join interface is incorrectly configured as g1/1 (20.20.20.2), which is an internal trunk and not the correct routed interface to the OTV transport network. Because the join interface does not face the multicast-enabled transport, OTV cannot establish adjacency and the VPN state remains DOWN. Correct configuration should use: otv join-interface GigabitEthernet1/0

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