So I have two -current i386 machines in a rack next to one another on an 
Extreme Summit switch.  One machine has an fxp0 and the other a vr0. Both
are set to 100/full, the switch is on auto and acknowledges the current
setting of 100/full on each of the two ports.

 Port Tx Error Monitor                                 Fri Nov 7 09:01:00 2003
 Port      Link         Tx    Tx          Tx            Tx        Tx
           Status       Coll  Late Coll   Deferred      Error     Parity
 
===============================================================================
 spooge    ACTIVE          0          0          0          0          0

 Port Rx Error Monitor                                 Fri Nov 7 9:01:19 2003
 
Port      Link        Rx      Rx      Rx        Rx     Rx        Rx        Rx
          Status      CRC     Over    Under     Frag   Jabber    Align     Lost
 
===============================================================================
 spooge    ACTIVE        0        0        0        0        0        0    0


As you can see, no collisions or other errors. netstat -in reports the
same.

The problem is that while the machine with the fxp0 in it can do line
speed to a 3rd machine (a Sparc of some sort), the machine with the vr0
can't seem to get >500KB/sec to the machine with the fxp0 or the sparc.

There is no ipf or altq in the way here. 

Is there some known problem with vr interfaces that we know they're a
POS? Or is there some known defect in our code?  Any suggestions?

vr0 at pci0 dev 18 function 0: VIA VT6102 (Rhine II) 10/100 Ethernet
vr0: interrupting at irq 11
vr0: Ethernet address: 00:e0:4c:a3:6d:89
ukphy0 at vr0 phy 1: Generic IEEE 802.3u media interface
ukphy0: OUI 0x0002c6, model 0x0032, rev. 5
ukphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

Now, the only suspicion that I have is:

com3 at puc0 port 0: interrupting at irq 11
uhci0: interrupting at irq 11
vr0: interrupting at irq 11

but I'm using neither com3 or uhci at the moment... That shouldn't 
cause a problem anyway.