Changes to routing table with multilink PPP

I've converted a T1 connection between two sites to use multilink PPP, in preparation for putting in a second T1 between the sites. As part of this change I moved the IP address (, with a /30 netmask) from the serial line (serial1/0) to the multilink interface (multilink1).

This caused a change in the routing table that I didn't expect. Before the multilink config, the relevant routing table entries looked like this: is subnetted, 9 subnets C is directly connected, Serial1/0

The other 8 subnets on were also /30s. But after the switching to the multilink the routing table now looks like this: is variably subnetted, 10 subnets, 2 masks C is directly connected, Multilink1 C is directly connected, Multilink1

So apparently what's happening is that not only is the route for the network on the multilink interface itself being added to the routing table (as I expected), but also another route for the IP address of the router on the *other side* of the multilink interface (

Is this expected behavior? This is on IOS 12.3(17a), by the way. If it's not expected behavior, any ideas why it would be happening?

- John

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John Caruso
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this is default behaviour for PPP IPCP.

to disable this behaviour:

int no peer neighbor-route

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Yes, that was it, thanks. I see a lot of references to it now that I know what to look for (so often the case with Cisco).

One point for anyone reading this in the future: adding these statements to the config is not enough to get rid of the peer's /32 route once it's infested your routing table--you have to bounce the interface.

- John

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