[NTLUG:Discuss] Dual Nic's

[MadHat]

On Mon, 2003-09-15 at 11:18, Thomas Cameron wrote:
> I hope that I am just stupid and missed something, but I tried a similar
> setup and the Linux box tanked.  Two IP addresses on the same subnet does
> not seem to be do-able.  I've had problems in Win2K and RH9 trying it.  The
> box just seems to get confused and doesn't talk to anyone.

Its probably because you had 2 default routes for the same subnet.  If
you set the sub net mask for one of them to 255.255.255.255 it will
work, more or less.

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt
Iface
172.21.142.0    0.0.0.0         255.255.255.0   U         0 0          0
eth0
0.0.0.0         172.21.142.1    0.0.0.0         UG        0 0          0
eth0

So if I added eth1 on the same subnet with the same subnetmask, I would
end up with 2 entries for the same route, but for 2 different
interfaces, and that doesn't work.  Now once you had both working, you
would need to set up static routes to decide which interface would
handle which routes, or run a routing protocol to determine, but then
you are running a router and not a desktop/server.

-- 
MadHat at Unspecific.com
`But I don't want to go among mad people,' Alice remarked.
`Oh, you can't help that,' said the Cat: `we're all mad here...'
   -- Lewis Carroll - _Alice's_Adventures_in_Wonderland_