[cisco-voip] Phones on wrong VLAN?

[Mike Newell]

We have a weird problem...

About 10% of our phones on one of our networks get the wrong VLAN when
they boot up.  If we continually reset them eventually they get on the
right one; then every now and then one will spotaneously flip back over to
the wrong VLAN again.  We've opened a TAC case (#601492441) but so far
their recommendations point to errors that have conditions unrelated to
ours...

In specific we have a bunch of 7970s attached to a pair of Catalyst 6509
switches.  The ports are set up in dual-access mode with a voice and
access VLAN set.  As far as we can tell data throughput on the ports is
reasonably light; no broadcast storms, dropped packets, etc.  The phones
are never in use when they flip (usually they flip in the night; bored
maybe?)  We're running 6.0.2SR1.

What we see happen is the phones issue a DHCP request on the access VLAN
(not the voice VLAN).  The DHCP server cheerfully gives them an address
and they register.  After a while they seem to figure out they are in the
wrong VLAN and switch to the voice VLAN, issue a DHCPRELEASE for the
original address, then re-register with the new address.

The really weird thing is it's not consistent.  It's only happening with a
few phones, and then only occasionally.  It's often enough to be annoying
but not often enough to force us to upgrade all the phones (we have a long
painful process for putting out new software releases, and they JUST NOW
finally ordered our lab).  It doesn't happen at all with any of our phones
connected to our 3560 switches.

Anyone seen this?  Any ideas???

Thanks!!

Mike