My main computer/gateway has ix0, ix1, and vr0 interfaces.  With the cable
modem on vr0, things work great w.r.t. NAT on my home subnet.  If I connect
ix1 to the cable modem, and restart things, ipnat works  r e a l l y 
s l o w.  Like seconds/minutes between some keystrokes in a telnet
session.

  I know the ix* cards aren't exactly modern, but I know they can keep
up with 180KB/s local downloads, and the CPU can obviously keep up with NAT
when I use a different interface.  As another experiment (actually, this was
the first one), I tried setting up another machine as my gateway -- it has ix0
and ix1 only.  NAT didn't work very well on ix1 there either (same
slowness symptoms).

  BTW, I did remember to change my NAT rules in /etc/ipnat.conf when I
changed the interface.  Are there any other common gotchas?  It almost
seems like there's some sort of timeout that every single packet is
experiencing.

  Thanks in advance.

  Brian Grayson