I have two EX 4300 acting as a core for a building. Does NSR needed in a virtual chassis to preserve l3 routing? At the momenti only have GRES configured. I thought NSR is needed only when a device have two built in RE.
YES you need to enable it
it copies all realtime information of routing protocols and Session and TCP info from the RE to the backup RE, thus BGP and OSPF and other sessions will not be reinitialized when there is a RE switchover
You need GRES/NSR only when you have dual RE.
Each of these two features does something different with regards to interfaces states or routing protocols states during a RE switchover.
Here is something about GRES:
And about NSR:
https://www.juniper.net/documentation/en_US/junos/topics/concept/nsr-overview.html=====If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.
Just to be clear Dual RE could be a virtual chassis as well as a single router with two RE? Am i correct?