failover of sort, using a rule 3

[snootalope]

Not even sure if this possible or not, but is it possible to use a rule that can send all traffic out one wic as long as it's interface is up, and in the event it's down, send it out another interface? I'm guessing this somekind of failover feature that we'd need to pay more for, but thought I'd check.

It's a cisco 1751 router if it matters. 1 WIC is the four port ethernet card, the other is a T1-WIC.

Thanks for any advice.

 

[baddos]

By default a route will be removed from the forwarding table if the interface it's used on goes down. So say route 0.0.0.0 0.0.0.0 1.1.1.1 and the interface 1.1.1.0 was on was down, that route would get nuked.

 

[burtsbees]

You would add a higher metric to the failover route. For example...
ip route 0.0.0.0 0.0.0.0 1.1.1.1
and another way it can get out would be via 2.2.2.2, and say this is the failover route. Then you would do this...
ip route 0.0.0.0 0.0.0.0 1.1.1.1
ip route 0.0.0.0 0.0.0.0 2.2.2.2 50
with the "50" at the end, specifying the higher metric and therefore less preferred route. If the 1.1.1.1 goes down, then 2.2.2.2 will automatically pick up, since 1.1.1.1 gets nuked out of the routing table, as baddos says. This is called a floating static route.

Burt

 

[snootalope]

awesome.. thanks fella's. I figured this was gonna be something we'd have to pay for!

So, using the example by burt:

ip route 0.0.0.0 0.0.0.0 1.1.1.1
ip route 0.0.0.0 0.0.0.0 2.2.2.2 50

If the preferred route is down for five minutes and comes back, would the traffic automatically begin using the preferred route again, or since it was nuked out of the routing table would I need to re-add it?

 

[burtsbees]

Not sure...ya got me on that one...best way is to do a shut and a no shut, forcing the interface to reset and thus causing it to rechoose the best default route.

Burt

 

[eclidad]

How does NAT come into play here. We are served by 2 ISPs. We use route maps to decide which NAT pool to use. For most of our browsing and downloads we pick an address from pool B and use ISP #2. If we need to get at our ftp/web server we use pool A. The ftp/web server routes out ISP #1. IT would seem as though that NAT needs to happen after the route has been selected but there's nothing that I can see in the route map setup to indicate this.

Curious minds want to know. Any references to cisco docs would be helpful.

Thanks,
- Joel