[c-nsp] Strange behavior with 12008

[Ed Ravin]

On Thu, Jan 19, 2006 at 11:42:08AM -0800, Erica wrote:
> ... 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.

Two possibilities - one, as already suggested, someone broke a netmask
somewhere, and two, there's a bad or flaky route processor somewhere
that needs kicking.  I've seen this a couple of times with one Tier1
provider where we got partial blockage, once for TCP and not UDP, once it
was for alternating blocks of 48 and 16 addresses (48 work, 48 don't work,
16 work, then 48 don't work, etc.) and so on.  All were resolved when
the provider finally faced facts and rebooted their router (or reloaded
an individual card).