On Mon, 19 May 2008, Hank Nussbacher wrote: Cisco TAC found that the one interface that worked didn't have uRPF enabled whereas the others did: ip verify unicast source reachable-via rx allow-default 170 What is amazing is that this caused deterministic pkt loss. I have removed it and pkt loss went away. Reapplied the ip verify and pkt loss still was 0! Truly amazing.
Any clues why this would happen? Thanks, Hank > We are encountering some very strange behavior on POS interfaces seated > inside eFlexwans on a 7613 with SUP720. On a 7613 running 12.2(18)SXE6b we > do not see any of this strangeness. On a 7613 running 12.2(18)SXF11 - we do. > > The strangeness is hard to define. It appeared first when we tried to bring > up a backup STM-1 circuit which hadn't been used in a year and would only > pass about 700kbps. We blamed the carrier but now suspect a subtle bug in > IOS. Other POS interfaces also show pkt loss, whereas one other POS > interface - which happened to be the only live one with constant moving > traffic does not show any strangeness. > > When doing ping from the router to the other side of the interface, we see > deterministic pkt loss like this: > POS3/0/1 > Sending 10000, 100-byte ICMP Echos to xxx.139.237.2, timeout is 2 seconds: > !!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!! > !!!!!.!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!! > !!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!!!!.!!!!!!!!!!!!!.! > > The drop on this link is periodic, it's not random, every 14th packet is > dropped. We have no rate limiting enabled. Depending on packet size of ping > - we get different deterministic results. > > After playing with the bad interface for a while (shut, no shut, sdh parms, > moved to another free POS port, SDH tester equipment, loopbacks, etc.), it > suddenly came alive and no longer lost any packets. > > Has anyone encountered anything similar to this? > > Otherwise, this is gonna be hell to debug with TAC. > > Thanks, > Hank > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
