Well, this was a new one for me. One way packet delay of around 20 seconds on a single link. I had never thought it was possible, but just when you think you've seen it all...
I have a customer with a number of sites, each with 2 x 3750 in a stack. Each stack will typically have four ethernet hand offs to Ericsson equipment which provides transparent circuits over microwave. One member of the stack will have two circuits towards one neighbouring site, the other member will have two circuits towards a different neighbouring site. The same microwave equipment provides all four circuits (potentially spread across different line cards though) although with different dishes to provide the appropriate directionality for the microwave. Each circuit has a single P2P VLAN configured on it. This generally works fine. Yesterday we had a very interesting scenario where at approximately 1200 the 3750s saw interfaces flapping on both circuits between two particular sites. From 1220, one of those circuits appeared to introduce delay in one direction of 18-23 seconds. This could be demonstrated with debugs of both CDP and ICMP traffic. The relevant interface at both ends were both manually shut/no shut and also err-disabled/no shut due to UDLD detecting a problem. I'm pretty sure all interface up/downs were seen by the 3750s at both ends. The microwave equipment is meant to relay up/down events that occur any where in the path to all ethernet ports so that is expected regardless of where the event actually occurred. It is currently not clear if the microwave equipment logged all those events or just the ones caused due to UDLD or manual action. Around 1500 we again saw interfaces flapping on both circuits between the same two sites. Around 1600 I checked the fault again and it had cleared. My assumption is that it cleared after the flapping. Ignoring the specifics of the up/down events and even if it was the Cisco or Ericsson kit that was at fault, has anyone ever seen packets held up for 20 seconds across a link? Cheers, Ray _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
