Exam 300-420 topic 1 question 219 discussion

Answer is C. The key is the "routing process" on R2 needing maintenance, which means the control plane will be down, but NOT the data plane. We can still move traffic through the data plane on R2 by way of NSF running on R1 and R3. The data plane on R1 and R3 needs to continue to forward packets even if they aren't receiving routing updates from R2. NSF will allow routers 1 and 3 to mark the routes previously learned from R2 as "stale" and continue to forward to them while the routing process is unavailable.

The graceful restart feature in OSPFv3 allows nonstop data forwarding along routes that are already known while the OSPFv3 routing protocol information is being restored. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/ip6-route-ospfv3-gr-rest-xe.html#:~:text=The%20graceful%20restart%20feature%20in%20OSPFv3%20allows%20nonstop,helper%20mode%20%28such%20as%20in%20a%20graceful-restart-aware%20device%29.

For achieving high availability and maximum uptime for the data plane between R1 and R3 in an OSPF network where the routing process on R2 requires maintenance, the solution to include is "nonstop forwarding" (NSF). Specifically, enabling nonstop forwarding on R3 would help maintain forwarding during the period when R2's routing process is undergoing maintenance. Nonstop forwarding ensures that the routers in the network continue to forward traffic even during control plane disruptions, such as when a router's routing process restarts or undergoes maintenance. This helps minimize the impact on the data plane and maintain connectivity.

Graceful Restart (GR) is available for OSPF, ISIS, EIGRP, LDP, and BGP. Non- Stop Routing (NSR) is available in Cisco IOS for ISIS and BGP.

Option B looks like the correct Answer but the question states "Data PLane" so Option C seems like the correct answer based on this - NSF is a feature that allows routers to keep on forwarding traffic (non stop forwarding) even in the event of a restart. This is done by separating the control and the data plane, having one process involved in building the routing table and another process in forwarding the packets. This feature takes advantage of CEF which updates the line cards with the information from FIB.

https://networklessons.com/cisco/ccie-routing-switching-written/ospf-graceful-restart#:~:text=How%20does%20it%20work%3F,called%20the%20graceful%20restart%20mode.

Souldhn't be c: " nonstop forwarding on R1 and R3"?