Losing routes !!

[Mike Hogsett]

I have a machine that has been running 4.8-RELEASE for months flawlessly.
I recently CVSup'd to RELENG_4_8 (now running 4.8-RELEASE-p8).

The machine is losing routes.  Specifically its default route and a route
to the lan of one of its own interfaces.  I can manually add the default
route back, but it only lasts about 20 seconds until it mysteriously
disappears.

The machine has an Intel 1000baseSX card that is sub-interfaced using
VLANs.  There are 9 vlan interfaces in use (vlan0 through vlan8).

It consistently loses its default route and the route to the lan
`connected' to vlan8.

Any suggestions how I can diagnose what is happening?

Thanks!

 - Michael Hogsett