How to Enable OSPF Graceful Restart on a Helper Router

A.

The correct command to enable the helper router to terminate the OSPF graceful restart process if it detects any changes in the LSA is C. nsf ietf helper strict-lsa-checking.

Here's an explanation of the command and its parameters:

• "nsf" stands for "non-stop forwarding," which is a feature that enables routers to continue forwarding packets while they are restarting or undergoing maintenance.
• "ietf" and "cisco" are two different standards for implementing the NSF feature. The "ietf" standard is based on RFC 3623, while the "cisco" standard is a proprietary implementation by Cisco.
• "helper" refers to the router that is providing NSF support to its neighbor.
• "strict-lsa-checking" is a parameter that specifies how the helper router should handle changes to LSAs (link-state advertisements), which are used by OSPF to describe the topology of the network. If strict LSA checking is enabled, the helper router will terminate the NSF process if it detects any changes to LSAs during the restart.

Therefore, the correct command to enable the helper router to terminate the OSPF graceful restart process if it detects any changes in the LSA is "nsf ietf helper strict-lsa-checking".