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Static Routes (Cisco)

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by techstop 1 view

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I'm working on a test lab with a couple Cisco 2503 routers with BRI interfaces, as well as a Teltone ISDN simulator, and a couple ISDN "modems".

I've entered several static routes to networks on the "other side" of the ISDN network.

As long as the static routes is something like this:

ip route 172.16.241.1 255.255.255.0 bri0

it works okay. Note that 172.16.241.1 is the address for the "other side's" bri0 interface (172.16.243.1 being on "my side").

However, if I REMOVE that route, and try to enter any other static route at all---regardless of source or destination used---it fails.

According to documentation, I should be able to do something like

ip route 192.168.1.0 255.255.255.0 172.16.241.1

And that should work because of my dialer map statement, which maps 172.16.241.1 to the router on the other side.

I can't figure why it works with the one static route entry (and then I can add, and reach, any other networks on the other side by adding statics for them, as well), but it won't work, or accept any static route entries, if I don't add that one line.

Any ideas from anyone?

Thanks in advance.

2 replies

by pkust

The most reliable method of doing static routes for BRI interfaces I have found is to have a static host route for the "far" end going directly to the BRI interface; then other routes using that far end IP address can be designed normally.

Try this combination:

ip route 172.16.241.1 255.255.255.255 bri0
ip route 192.168.1.0 255.255.255.0 172.16.241.1

Note: This approach is also found on some of Cisco's cookbook examples for configuring BRI interfaces.

Cordially,

Peter Nayland Kust
TEKMedia Communications
pkust@tekmedia.com
http://www.tekmedia.com

by techstop

You said it.

I mentioned in my original posting that the combination you mentioned worked. (I split it up in the original post, so maybe you didn't notice that.)

Even though I already said it, I appreciate your confirmation of what I had discovered. None of the Cisco examples I looked at showed that. All of them just had the second statement. So I thought it should work without the "ip route 172.16.241.1 255.255.255.0 bri0" statement.

Anyway, now that you've confirmed it for me, I'll go with that. This is a test lab situation, and I was just puzzled as to why it didn't work the way the ICND and the BCRAN books showed it.

Can you mention which books show the cookbook example that uses this approach?

Thanks VERY much for your input!

Rick Horowitz, MCSE, MCT, CCNA, LCP
TechStop Support Services
http://www.TechStop.com

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