Determining NHRP Registration Process Completion Issues

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The NHRP (Next Hop Resolution Protocol) is used in Dynamic Multipoint VPN (DM VPN) networks to resolve the next-hop information for routing packets to remote spoke sites. If the NHRP registration process is not being completed even after the IPsec tunnel is up, the following two commands can be used to determine the cause:

1. show crypto ipsec sa: This command displays the IPsec security associations (SAs) that have been established for a specific crypto map entry. It provides information about the security protocols, encryption algorithms, authentication methods, and other parameters associated with the IPsec SA. By examining the output of this command, you can verify that the IPsec tunnel is up and functioning properly.

2. show ip nhrp traffic: This command displays NHRP-related statistics and counters for the router. It provides information about the NHRP packets being sent and received, including the number of registration requests, replies, and errors. By examining the output of this command, you can determine if there are any issues with the NHRP registration process, such as a failure to send or receive registration requests or replies.

Therefore, options C and D are the correct answers: show crypto ipsec sa and show ip nhrp traffic. Option A, show crypto isakmp sa, displays the status of the ISAKMP security associations, which are used to establish the IPsec SA. Option B, show ip traffic, displays traffic statistics for various protocols, but does not provide specific information about IPsec or NHRP traffic. Option E, show dmvpn detail, provides detailed information about the DM VPN configuration, including the status of the IPsec and NHRP components, but is not as specific as the other two commands in identifying the cause of the NHRP registration issue.