Description of problem:

Since upgrading our RHEL4 boxes to the 2.6.9-34.EL kernel, we've experienced
problems with our virtual interfaces and VLAN tagged frames.  Before upgrading
to the kernel, our multi-homed box worked fine, dhcping for addresses on each
virtual interface.

Our two interfaces are eth0.75 and eth0.76, using a tg3 driver for an onboard
Broadcom Corporation NetXtreme BCM5751 Gigabit NIC.

After the kernel upgrade to 2.6.9-34.EL, eth0.75 is unable to DHCP for an IP
address.  The DHCP server never sees the DHCPDISCOVER.

However, eth0.76, also using tagged frames, is able to successfully DHCP for an
address.

Strangely, when I disable eth0.75 (using ONBOOT=no in ifcfg-eth0.75), and
restart the network service, eth0.76 can no longer DHCP.  Again, the DHCP server
never sees the DHCPDISCOVER.

I tried statically assigned an IP address, but the problemed interface still
wasn't able to see the network.  However, I am able to tcpdump, and I see the
apropriate ARP requests acrossed that tagged network.

I believe there is something wrong with the tg3 driver we are using for our NIC.
 I installed a PCI 3com NIC, setup virtual interfaces simularly, connected to
the same switch port as I was previously using, and virtual interfaces DHCP fine
with the latest kernels.

However, I tried downloading the source code for the latest tg3 driver from
broadcomm's website.  It compiled fine, but I continued to have the same problem. 

Version-Release number of selected component (if applicable):
2.6.9-34.EL and 2.6.9-34.0.1.EL.  This setup was working using 2.6.9-22.0.2.EL
and previous kernels.
 
How reproducible: Always

Here are the relevant files:

# more /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=localhost.localdomain
NISDOMAIN=<our_nis_domain>
GATEWAY=<our_gateway_ip>
VLAN=yes

# more /etc/sysconfig/network-scripts/ifcfg-eth0
# Broadcom Corporation NetXtreme BCM5751 Gigabit Ethernet PCI Express
DEVICE=eth0
ONBOOT=no
BOOTPROTO=none
PEERDNS=no
TYPE=Ethernet

# more /etc/sysconfig/network-scripts/ifcfg-eth0.75 
DEVICE=eth0.75
BOOTPROTO=dhcp
ONBOOT=yes
PEERDNS=no

# more /etc/sysconfig/network-scripts/ifcfg-eth0.76 
DEVICE=eth0.76
BOOTPROTO=dhcp
ONBOOT=yes
PEERDNS=no