up2date from behind corporate firewall

[pjain001 at covad.net]

I just installed FC3 on my work machine and up2date can't seem to get
through the corporate firewall.  The only outgoing traffic that's allowed
is on port 80.  up2date with RHN used to work without a problem.  Does
anyone know what port is being used with FC3 to get a list of the updates
and then grab the RPMs?

My proxy settings are correctly set.

Thanks
Pankaj