Connected routes 1

[JimboNJ]

Long time reader, first time poster here.

I'm trying to figure out the best way to stop this problem from happening. If we build a channelized T1 interface for a customer T1 with numbered interfaces, and the customer equipment has the wrong IP on it, it seems this makes our router add a route for that IP even though it doesn't match the interface.

Example-
Fake customer CPE is an Adit 600 with a 192.168.100.1/30 IP for a WAN address. Our Cisco serial interface is:
interface Serial0/0/0/3:0
description Test T1
ip address 209.204.92.229 255.255.255.252
encapsulation ppp
load-interval 30
no fair-queue
no cdp enable
end

Cisco5#show ip route connected
C 192.168.100.1 is directly connected, Serial0/0/0/3:0

The root of my concern here is a piece of CPE with an incorrectly numbered WAN interface bumped a customer today.

The prospect of access-listing every interface on the network is not appealing and I'm not sure that would stop the routing table entry from being created.

Thanks for any guidance you can provide.

 

[jneiberger]

This is happening because you're using PPP. PPP automatically adds host routes for the opposite side of a connection. Switch to HDLC or something else and it won't happen.

 

[jneiberger]

I guess I should clarify by saying that Cisco's HDLC is not necessarily compatible with the HDLC used by other vendors. Verify that it will work before you try it. I think there might also be a PPP command that turns off the addition of that host route, now that I think about it. I haven't had to know that in about seven years, so my memory is hazy.

 

[jneiberger]

Ah, here it is: no peer neighbor-route.

Add that command to your interfaces and see if that fixes your problem.

 

[JimboNJ]

Fantastic, this looks like exactly what I was looking for. I knew there had to be a command for this, but it has been some time since I was deeply involved with T1 buildouts.

Many thanks jneiberger!