Does anyone know what internal criteria various routers use to sense when their WAN connection has gone down when configured for VRRP, in order to then decide to switch over from the master to the backup router? I have some thirdhand reports that Fortigate devices simply use the presence or absence of an internal route to a specific external subnet or host (e.g. 4.2.2.1). This to me seems wrong – because the route could still exist on the master, but the actual connectivity is not there, which would mean that the master would not fail over to the backup.
Curious if anyone knows the internal implementation details of various routers (e.g. FG, Cisco).
Forgive me if this has already been answered, or if my question doesn't quite make sense. I'm kind of a network n00b.
Best Answer
First Hop Redundancy Protocols Configuration Guide, Cisco IOS XE Release 3S