Implementing Cisco Enterprise Advanced Routing and Services (ENARSI) — Question 284

A newly installed spoke router is configured for DMVPN with the ip mtu 1400 command. Which configuration allows the spoke to use fragmentation with the maximum negotiated TCP MTU over GRE?

Answer options

• A. ip tcp adjust-mss 1360 crypto ipsec fragmentation mtu-discovery
• B. ip tcp adjust-mss 1360 crypto ipsec fragmentation after-encryption
• C. ip tcp payload-mtu 1360 crypto ipsec fragmentation after-encryption
• D. ip tcp payload-mtu 1360 crypto ipsec fragmentation mtu-discovery

Correct answer: B

Explanation

The correct answer is B because the command 'crypto ipsec fragmentation after-encryption' allows for fragmentation of packets after they have been encrypted, which is necessary for maintaining proper MTU sizes in a GRE tunnel. The other options either use 'mtu-discovery', which does not specify fragmentation post-encryption, or utilize 'payload-mtu', which is not applicable in this context.