Hi nanog, Strange thing happens everyday. When I were troubleshooting yestoday, I found a ping to my local serial interface (no matter it's 155M POS, or 2M Serial interface) takes nearly twice delay compared with a ping to the remote side of the serial interrface ! When I trace to my local serial interface, I got the first hop to the remote end, then second hop back to my local interface ! For example, 202.97.2.1 is local serial interface, while 2.2 is remote side. A trace on 2.1 to 2.1 first go to 2.2, then back to 2.1. And this situation can be verified on both side. Have you ever seen this situation ? Is it due to our misconfiguration? or it's sheerly a mis-display of result in Cisco box (can't believe it) The background is: we're using ISIS as IGP, and utilized level-1/2 link. thanks for any input. regards, Yu Ning ------------------------------------------- (Mr.) Yu(2) Ning(2) ChinaNet Backbone Operation Networking Dep.,Datacom Bureau China Telecom.,Beijing(100088),P.R.C +86-10-66418121/66418122/66418123(fax) -------------------------------------------