I have the new cisco 1841 router with 1 ethernet and 1 serial WAN interface card connected to a leased line modem. I noticed something weird while doing some troubleshooting.
If I unplug the LL modem, I can still ping the serial interface while I am telneted to the router. I even tried disconnecting the cable from the serial int, it still pings! Finally, I gave the command to shutdown the serial int and guess what? I can still ping the serial int IP!
I tried this out on a 1720 router and it does not ping the serial int, which is normal.
Can anybody explain please? It's driving me nuts.