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New Member

Router failover preference

Hello and thank you in advance for any feedback.

I have a 2621 Router in one of my departments located in remote campus building. The primary link is a laser link that goes down when we have a decent amount of fog. We have a T1 backup, ISDN (which I plan on removing) and an FXO line.

We have tested all lines on their own and they work properly. This morning I noticed that when the laser link went downthe ISDNs picked up not the T1. I don't know why this would happen. Is there some way to set preference of fail-over connections?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Router failover preference

There are ways to set preference for failover. If you would post the config of the router we would understand better what you are dealing with and be in position to make better suggestions.

In general there are several ways to specify failover and to establish preference. One option is to configure the primary link with the backup interface command which specifies the failover mechanism and inherently sets preference.

Another option and more generally used are to configure floating static routes. As long as the primary link is up there is some route in the routing table (it might be learned from a dynamic routing protocol or it might be statically configured). When that route is withdrawn from the routing table (failure of the primary interface) the floating static is used.

Another option is to establish failover (and preference) via dynamic routing protocols. If the dynamic routing protocol advertises some destination with a more favorable metric that becomes the primary path. If the dynamic routing protocol advertises some other path with a less attractive metric then it becomse the backup path.

So give us some more information about your situation and we will see if we can give you good suggestions.

HTH

Rick

2 REPLIES
Hall of Fame Super Silver

Re: Router failover preference

There are ways to set preference for failover. If you would post the config of the router we would understand better what you are dealing with and be in position to make better suggestions.

In general there are several ways to specify failover and to establish preference. One option is to configure the primary link with the backup interface command which specifies the failover mechanism and inherently sets preference.

Another option and more generally used are to configure floating static routes. As long as the primary link is up there is some route in the routing table (it might be learned from a dynamic routing protocol or it might be statically configured). When that route is withdrawn from the routing table (failure of the primary interface) the floating static is used.

Another option is to establish failover (and preference) via dynamic routing protocols. If the dynamic routing protocol advertises some destination with a more favorable metric that becomes the primary path. If the dynamic routing protocol advertises some other path with a less attractive metric then it becomse the backup path.

So give us some more information about your situation and we will see if we can give you good suggestions.

HTH

Rick

New Member

Re: Router failover preference

Thank you for the input. I also received some help along those lines from an old colleague.

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