Doc says dialer watch uses routing "updates" to determine when to raise and drop dial backup. Anyone know if that truely means updates so that the primary route does not have to be a better route than the backup? Or do I still need to control the weight of the backup route so it will disappear when the primary recovers?
All you need to do is under the backup interface add the command 'dialer watch-group 1' and under config t 'dialer watch-list 1 ip x.x.x.0 255.255.255.0' (the route[s] to watch). As long as that route is in the routing table (ie learned from the routing updates) your backup won't kick in/dial out. Once that route drops from the routing table, the backup interface kicks in/dials out.
I follow how the backup takes over. I'm trying to figure out how the primary route will take over when it recovers. What if the backup route is a better route? The primary wont replace it in the route table. Remember this is routing protocol independent and can span different routers so it could be a smaller pipe with less hops,etc. In cases where the backup router is not the same router that has the primary link dialing direct to the remote will give it a better route. So is it watching just for an update, even if the route is not a better one. Or does the primary route have to be in the route table? That could mean I have to weight the routes depending on the circumstances of the circuits and the routing protocol being used.
When we talk routes the route in the dialer watch must match exactly (ie same network and same mask) as the route in the table. Otherwise it's considered a different route. So the route/network is the same. Also, why different routing protocols over different links? If you have ospf over your primary serial line and eigrp over the backup bri (ie the bri line is preferred), you have an unusual network. So admin distance shouldn't be a factor, they should be the same. And it would be rare for a backup link to have better metrics or bandwidth than the primary link, otherwise why would it be a backup? So after all this it would be unusual to have the situation you describe.
If the primary route has better metrics, when it enters the routing table the backup link drops. This is the case in most situations.
But let's assume that the metric is better on the backup for arguments sake. Never tested it but I will to see if the decision to flip over to teh primary is based on metric or if it's based on updates from a different interface.
Actually the separation of the backup link to a different router is one of the advantages of dialer watch over the backup interface feature. The backup router can be many hops away from the router with the primary link. The simple example in the Cisco cd shows routers A and B on a lan with router A having the primary link to C and B having a dial backup to C. If you are running RIP on all links (not different protocols on each link, just "any" one routing protocol) then once B is active in backup mode it has the best link, even if A recovers its link it is two hops from B but B has its dial up link that can get there in one hop. A's route will never get put into the routing table on B. So either you need to wieght the routes or it is keying on routing update packets, not the route table.
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