Primary Requirement for Deploying OSPF Graceful Restart on a Router

B.

OSPF graceful restart is a feature that allows a router to continue forwarding packets during the restart of its OSPF process. This feature is particularly useful in networks where there is a high level of availability and downtime must be minimized.

The primary requirement for deploying OSPF graceful restart on a router is that the adjacent router must support graceful restart helper mode. When a router restarts, it sends a graceful restart message to its adjacent routers. If an adjacent router supports graceful restart helper mode, it will keep forwarding packets on behalf of the restarting router for a certain amount of time, typically up to a minute or so.

During this time, the restarting router can rebuild its OSPF database and reestablish adjacency with its neighbors. Once the restart is complete, the restarting router sends a graceful restart acknowledgment message to its adjacent routers, indicating that it is ready to resume normal OSPF operation.

Aggressive routing protocol hellos and keepalives are not a requirement for deploying OSPF graceful restart, but they can help improve the speed of the graceful restart process. Fast Layer 2 down detection can also be useful in detecting link failures and triggering the graceful restart process.

Enabling adjacent routers to forward traffic during the failure is not a requirement for deploying OSPF graceful restart, but it is a desirable feature that can help improve network availability. This feature is typically achieved through the use of redundant paths and fast convergence protocols such as Cisco NSF and NSR.