Exam 300-420 topic 1 question 59 discussion

C => stateful switchover

The correct answer is C. Stateful Switchover (SSO). Stateful Switchover (SSO) is a feature that allows graceful restart to recover from a processor failure in a network device. SSO enables a device to maintain its forwarding capability while recovering from a processor failure, minimizing the impact on network traffic. This is accomplished by synchronizing the control plane information between the active and standby processors in the device. In the event of a processor failure, the standby processor takes over the control plane functions without causing any disruption to the forwarding plane.

Cc is correct

This is a tricky question. In the OCG pg 168 it states "Graceful Restart (GR), also known as Non-Stop Forwarding..." So Graceful Restart and Non-Stop Forwarding are one in the same. Now looking at the this site https://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html it states "SSO is a prerequisite of NSF". So going by what the OCG said above, and after reading the link above, what we can conclude is SSO is a prerequisite of Graceful Restart.

CCNP Enterprise Design ENSLD 300-420 Official Cert - Page 220

I say C. CEF is required for uninterrupted traffic flow, yes, but.... SSO is required for GR to work at all and this is what is asked in the question.

C is answer

"Cisco NSF is supported by the BGP, EIGRP, OSPF, and IS-IS protocols for routing and by Cisco Express Forwarding (CEF) for forwarding"

A is correct... (although it migh seem strange...) I found this: In Cisco networking devices, packet forwarding is provided by Cisco Express Forwarding. Cisco Express Forwarding maintains the FIB and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. The ability to continue packet forwarding ----------------------------------------------------------------- eliminates downtime during the switchover.----- i find it here: https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd801dc5e2.html

C is 100% correct

C is correct

C ! The Stateful Switchover (SSO) feature works with Nonstop Forwarding (NSF) in Cisco software to minimize the amount of time a network is unavailable to its users following a switchover. The primary objective of SSO is to improve the availability of networks constructed with Cisco routers.

Is A: Cisco Express Forwarding for NSF A key element of NSF is packet forwarding. The OSPF protocol depends on CEF to continue forwarding packets during switchover while the routing protocols rebuild the Routing Information Base (RIB) tables. Once OSPF has converged, CEF updates the Forwarding Information Base (FIB) table and removes stale route entries. CEF then updates the line cards with the new FIB information. CEF maintains the FIB and uses the FIB information that was current at the time of a switchover to continue forwarding packets during the switchover. This feature reduces traffic interruption during the switchover.

Easy. C SSO

I think it is A. Cisco Nonstop Forwarding does not maintain a continuously active control plane during switchover. Instead, the forwarding plane uses known routes while the routing protocol information is being restored after switchover. In Cisco networking devices, packet forwarding is provided by Cisco Express Forwarding. Cisco Express Forwarding maintains the FIB and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. The ability to continue packet forwarding eliminates downtime during the switchover. Each protocol depends on Cisco Express Forwarding to continue forwarding packets during switchover, while the routing protocols rebuild the Routing Information Base (RIB). https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd801dc5e2.html

I don't know.. It's probably "A" belong this : https://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/high-availability/solution_overview_c22-487228.html GR and NSR, when coupled with SSO provide the foundation for fast recovery from a processor failure and allow the use of ISSU to perform software upgrades with little downtime. SSO is necessary to handle other non routing protocol related items needed for the router to operate following a switchover. These include syncing the complete router configuration, Cisco Express Forwarding (CEF) forwarding entries and other needed information to the standby processor.

C is correct! - GR is the only feature that interacts with peer network devices, all other features (SSO/NSF/NSR) are internal to the router and therefore don’t require standards. Source: https://archive.nanog.org/meetings/nanog42/presentations/Weissner_SSO.pdf