Next-hop IP shows from the output of "show arp" but it's not reachable

[F Martinez]

Hi,

We were trying to upgrade a router - specifically a C871 to C881. We have a DSL circuit connected to the old router  (C871) and everything is working fine - I can ping the next-hop device and I can get to the Internet. We swing over the DSL circuit to the new router (C881) and configured it the same as the old one (same IP address on the public interface and same next-hop IP for the default route.)

Now, the problem is, I CANNOT see my next hop IP address by doing a "show arp". I verified that I was seeing the same device that was connected to the old router by looking at the MAC address. But STILL I cannot ping my next-hop IP.

Has anyone experienced this before? This is the first I encountered this issue.

Thank you for your help in advance!

[Richard Burts]

I have seen situations which might be similar to this where the ISP device has leaned the MAC of your old device and does not want to communicate with the new device. Sometimes it can be resolved by power cycling the ISP device. Or perhaps you may need to discuss this with the ISP can see if there is something that they need to do.

HTH

Rick

[F Martinez]

We already tried power cycling the ISP device - it didn't work. Anyway, I think you are right, we need to discuss this with the ISP.

Thanks so much Rick!