The difference between SSO/NSF(GR) and NSR

[mhiyoshi]

Hello

I have a question about the difference between SSO/NSF(GR) and NSR.

In my understanding SSO/NSF is stateful switchover from Active to Backup
Mainly take over the startup configuration and it keeps the FIB TCAM table and so on.
But this protocol needs to re-establish the routing table and topology database etc.

But if NSR functions when stateful switchover happens then it takes over routing table
and topology database etc. right? 

If so, I think BGP peer down/up (flapping) , OSPF/EIGRP neighbor state change does not happen right?

[pantp]

Are you talking about SSO/NSF(GR) as NSF(GR) Non-Stop Forwarding(Graceful Restart) is quite different from NSR (Non-Stop Routing)?A bit confusing…

[mhiyoshi]

Hi, I am so sorry, it is SSO/NSF vs NSR which I have modified the above mistakes.

[Giuseppe Larosa]

Hello @mhiyoshi ,

>> If so, I think BGP peer down/up (flapping) , OSPF/EIGRP neighbor state change does not happen right?

if using Graceful Restart the local device before route processor switchover sends out protocol specific messages asking for a grace period. It is telling the neighbors that is going to perform  RP switchover and it may be not able to send out hellos or other keepalive messages during the grace time interval.

The neighbors devices will hide the fact that local node control plane is doing switchover and they still use the local node as a possible nexthop for transit traffic according to the FIB.

Only if a topology change occurs during the grace time interval the neighbors will turn down the neighborship.

SSO = Stateful Switch over is a redundancy strategy within a node with two RPs

NSR features should be different in the sense they act within the single node without involving neighbor devices.

So NSR occurs between RPs in a single node.

see also this related thread. It looks like that NSR does not apply to VSS or SVL pairs for BGP

https://community.cisco.com/t5/routing/bgp-sso-with-nsr/m-p/4734760

Hope to help

Giuseppe