MTU problem between 10/100 & Gigabit cards

HI Group,

I have been running a VLAN configured system for some years using 10/100 
Sundance driver cards without a problem.  I recently tried on a HP 
proliant server using gigabit cards and found a problem related to the 
MTU size for the interface I an using.

The 10/100 cards seem to need a MTU of 1504 bytes, but this size does 
not work with the e1000 gig cards, or the US robotics, Dlink DGE, 
broadcom etc.  I have to move the MTU down to 1500 to make fragmentation 
work and allow it to pass the larger packets.

Is this what I should expect from the e1000, broadcom, R8169 drivers for 
gigabit cards?

The 10/100 drivers are the sundance driver.  I am using Allied telesyn 
8000s/24 switches to detag the incoming tagged data stream and a PC on 
the unagged port of the allied switch.

2.6.21 kernel based on fedora 5.
vconfig version vconfig-1.9-2.i386.rpm




-- 

Gary