Ever wonder what this output meant?
R1# show ip protocols
*** IP Routing is NSF aware ***
So I'm Currently reading up on NSF/SSO for HA campus design and MPLS PE networks.
I was actually reading up on OSPF LLS (RFC5613), when I discovered that Cisco uses the LLS field to implement NSF (Cisco Non-Stop Forwarding Awareness) in OSPF, EIGRP, BGP and IS-IS.
In HA deployments, NSF provides forwarding for L3, and SSO provides forwarding for L2
So NSF basically works with dynamic routing protocols, but also HSRP.
FHRP - SSO Aware HSRP:
http://www.cisco.com/en/US/docs/ios/12_2s/feature/guide/fshsrpss.html
Configuring NSF with SSO Supervisor Engine Redundancy:
http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/31sg/configuration/guide/NSFwSSO.html
By now you're probably wondering how this works together with BFD? Me too. Pete Welcher at Netcraftsmen has an excellent article putting NSF, SSO and BFD in perspective:
http://www.netcraftsmen.net/component/content/article/68-network-infrastructure/784.html
By the way, since we're on the topic of layer 2 redundancy, make sure to check out Cisco's "Switching Kitchen", pretty good stuff :-)
http://www.cisco.com/en/US/prod/switches/sk_index.html
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