[c-nsp] Strange behavior with 12008

[Erica]

Hi All

Here's the situation.  Last week we suddenly lost connectivity to a website
on provider A's network.  When we started investigating the issue we
discovered that when they were trying to talk to us, they were stopped at
our providers router, with what looked like a ACL blocking traffic from that
particular IP.  We checked through all the ACL's on the interface and found
nothing that should be blocking their IP's.  More investigation has found
that we can get to all odd IP addresses in their blocks, but none of the
even IP addresses.  For example, xxx.xxx.xxx.66 is not accesible to us, but
xxx.xxx.xxx.67 is.  The route path also is currently symmetrical.  The
router in question that we are passing through is a 12008 running 12.0 (28)
S with several GE-GBIC-SC-B= cards.

My provider is completely stumped, as no one they know has ever seen this
type of behavior.  I thought I would help them out and see if anyone here
had come across this type of thing before.

Many thanks for your input.

Erica