A network engineer configures a new GRE tunnel and enters the show run command. What does the output verify?

Question

Exhibits

Options

• AThe tunnel will be established and work as expected
• BThe tunnel destination will be known via the tunnel interface
• CThe tunnel keepalive is configured incorrectly because they must match on both sites
• DThe default MTU of the tunnel interface is 1500 byte.

• A
  6% (1)
• B
  89% (16)
• D
  6% (1)

Explanation

GRE Tunnel Configuration Explanation

Option B is correct because show run only displays the static configuration as entered by the engineer - it confirms that the tunnel destination IP address is configured on the interface, but it cannot verify whether that destination is actually reachable in the routing table; the tunnel destination is simply "known" as a configured parameter on the tunnel interface itself.

• Option A is wrong because show run only shows configuration - it cannot confirm the tunnel is operationally up or functioning correctly (use show interfaces tunnel or show ip interface for that).
• Option C is wrong because show run doesn't evaluate whether keepalive values are mismatched with the remote peer - it only shows the local configuration, and GRE keepalives don't actually need to match on both sides to function.
• Option D is wrong because the default MTU on a GRE tunnel interface is 1476 bytes, not 1500 - GRE adds a 24-byte header overhead, reducing it from the standard Ethernet MTU.

Memory Tip: Think of show run as a "recipe card" - it tells you what ingredients (settings) are configured, but not whether the dish (tunnel) is actually cooking (operational). Always use show interfaces commands to verify live tunnel status.

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