Apologies for this question being a little long....
Just looking into the communities thoughts around some best practices around configuring VRRP.
By default the preempt delay is 0 seconds and the preempt to master would therefore be 3 hello's, which are sent every 1 sec. So my question is would a 3 second preempt be deemed sufficient? I've seen some set to 90 seconds, the logic for that is giving the network a chance to stabilise before going to master to stop flapping. Is there a formula you could use, what if you have more than 2 routers in the VRID.
This article with VRRP and FREB shows a prempt delay of 5 seconds:
In EOS I have in the past turned accept-mode on so that you are able to ping the VRRP VIP address, but in EXOS you do not need to do this. So wondering what other practical / best practice reasons there would be for turning it in. One example might be to support NTP over the VIP as per the following GTAC article:
This was mentioned above, but given its own heading for comment. In that example preempt delay was set to 5 seconds, so just wondering if the inclusion of fabric routing, and even the number of participating routers in the same VRID should be something to consider?
VRRP can be tracked via pings, IP routes and VLANs. So there is probably some obvious aspects of when that might be a good idea, but interested in some practical examples and / or best practices. As as an example the GTAC case below shows how to configure VLAN tacking if a VLAN fails so that it will failover to the other one, which sounds great but could that be considered good practice to do that on every VLAN?
An explanation for this is given here:
I can see this possibly making sense when using fabric routing mode and when multiple routers are in the same VRID. In fabric routing mode with MLAG my perception would be that traffic could end up at any switch in the MLAG pair, determined by the hashing algorithm configured on the LAG and then be routed from there. Both routers would essentially be advertising the same subnet so asymmetric routing could take place as traffic could land back at the other router (other switch in MLAG pair). Whether that actually matters though I don't think, because the switch would see the device directly attached through the other link in the LAG and therefore directly forward the request onto the client instead of passing it back to the originating router.
Interested in your thoughts.
Many thanks in advance