After a series of unexpected device failures on the network, a Cisco engineer is deploying NSF on the network devices so that packets continue to be forwarded during switchovers. The network devices reside in the same building, but they are physically separated into two different data centers. Which task must the engineer perform as part of the deployment?
In a Cisco networking device, Cisco Express Forwarding (CEF) is essential for packet forwarding and maintains the Forwarding Information Base (FIB). During a switchover, CEF uses the current FIB information to continue forwarding packets uninterrupted, thereby reducing traffic disruption. Implementing CEF ensures that packets are consistently forwarded during failures or router switchovers.
D - Cisco Express Forwarding Study the link below It is not necessary to use OSPF, you can also use EIGRP or BGP so that is not the correct answer but "so that packets continue to be forwarded during failovers" you use Cisco Express Forwarding (CEF). "Cisco Express Forwarding A key element of NSF is packet forwarding. In a Cisco networking device, packet forwarding is provided by Cisco Express Forwarding. Cisco Express Forwarding maintains the Forwarding Information Base (FIB), and uses the FIB information that is current at the time of a switchover to continue forwarding packets during a switchover, to reduce traffic interruption during the switchover." https://www.cisco.com/c/dam/en/us/td/docs/switches/lan/catalyst9400/software/release/16-6/configuration_guide/stck_mgr_ha/b_166_nsf_sso_9400_cg.html
From Cisco digital learning library, why no link: NSF-capable and NSF-aware peers cooperate using Graceful Restart extensions to BGP, OSPF, IS-IS, and EIGRP protocols. .... With the introduction of the LR-bit, an OSPF Cisco NSF router can discern whether an OSPF neighbor is capable of supporting its Cisco NSF procedures. When OSPF is operating and receiving hello packets with the presence of the LR-bit from its neighbors, it knows that the neighbor is NSF-aware and can execute the Cisco NSF procedures.
Quote is from https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd801dc5e2.html
Comments for nottoday2077 are indeed an OPTION if you use OSPF but you can also use BGP or ISIS. I believe D is correct because whichever protocol you use "CEF is a mandatory prerequisite for NSF. "
The question said that the engineer is deploying NSF, so we can assume that CEF is already implemented, but without BGP/OSPF/IS-IS/EIGRP, I don't think it will work.
ANS is D: For NSF operation, routing protocols depend on Cisco Express Forwarding to continue forwarding packets while routing protocols rebuild the routing information. https://www.cisco.com/c/dam/en/us/td/docs/switches/lan/catalyst9400/software/release/16-6/configuration_guide/stck_mgr_ha/b_166_nsf_sso_9400_cg.html
B is correct. The only logic is that they can have connectivity during RP switchover between the campuses if they reside in a different location.
For option B is more logical. Option A: Just by learning the Active and Standby state of the failover peer via L2VPN won't help to continue forwarding the traffic during switchover. Option C: Implementing VRF doesnt make sense Option D: CEF by default is already implemented. OSPF can use LSA 9 to inform its peer about the switchover.Type-9 LSAs are send to a neighbor with the GR flag set, as a part of the graceful-restart process. Devices must be NSF aware.
For this particular scenario since devices are separated in two DCs in different floors, the best option to work with NSF seems to be a L2VPN with a primary and backup link to converge fast. OSPF could be an option if using a failure detection mechanism like BFD, but it does not say it has it. CEF is a default protocol and works well with SSO for redundant supervisor modules on RP switches, but can't help much if the whole device go down. And I don't see how the VRF's option could possible help, again if the whole device fail. I go by option A, assuming we have redundant paths across those Data Centers, which is a MUST on today's networks.
This questions doesn't make sense if it's about NSF. NSF does not help forwarding between separated devices as far as I am aware. Cisco says "The main objective of Cisco NSF is to continue forwarding IP packets following a route processor (RP) switchover. Usually, when a networking device restarts, all routing peers of that device detect that the device went down and then came back up" Any other ideas?
Yeap, it doesn’t make any sense at all…