[c-nsp] Strangeness with eFlexwan POS ports on 7600

[Hank Nussbacher]

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