Refer to the exhibit. An administrator is troubleshooting network issues on a customer's network PE1 cannot form an LDP relationship with PE2 using LDP ID 192 168.1.1. Due to this connectivity issue,

Question

Exhibit

Options

• AConfigure PE2 to automatically select its own LDP router ID with 192.168.1.1.
• BCreate a targeted LDP session on PE2 to override the missing routing table entry on PE1.
• CConfigure PE1 with a static route to 192.168.1.1.
• DEnable LDP session protection on the link that P1 uses as the next hop to PE2.

• A
  4% (2)
• B
  2% (1)
• C
  83% (40)
• D
  10% (5)

Explanation

LDP (Label Distribution Protocol) sessions are established using the LDP Router ID, which is typically a loopback address. For an LDP session to form, each router must be able to reach the other's LDP Router ID in its routing table - LDP uses the Router ID as the destination for TCP session establishment. If PE1 cannot find a route to PE2's LDP Router ID (192.168.1.1), the TCP session (port 646) that underpins LDP cannot be established. Configuring a static route on PE1 pointing to 192.168.1.1 resolves the reachability issue and allows LDP to form. Option A is incorrect because auto-selection of LDP Router ID on PE2 would not help if PE1 still cannot reach it. Option B (targeted LDP session) still requires IP reachability to the LDP Router ID. Option D (LDP session protection) protects an existing session from going down, but cannot create a session that never formed due to missing routing.

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