Re: Multiple ethernet cards

[Johan Ehnberg <johan@ehnberg.net>]

I've been experimenting with this stuff, too. So maybe I can help you

> I put two ethernet cards in my pc. However, i can't
> ping a remote host from both interfaces (eth0,eth1, after
> swapping the cable over).

I assume you mean a computer that is not in your own network. If that is 
the case, you are completely right. To reach a computer beyond the 
specified routes in your routing table, you have to specify a default 
route. This however, is only possible to specify for one inteface as 
long as you use the standard 'route' tool. Try the iproute package and 
read Advanced Routing HOWTO on tldp.org. But I don't see why you need 
this complex setup.
If the "remote host" is a computer at your LAN, then you've got 
something set up wrong.


> If i disable one interface, then i can ping from the
> other. Both cards are pci of different brands.

By disable, do you mean a) ifdown or do you also b) remove the module? 
The difference could be a) routing problems and for b) rescource conflicts.


> I've tried giving both cards the same address and
> different addresses.

> I think it's because of the routing. netstat -rn:
>
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   Iface
> 210.50.118.58   0.0.0.0         255.255.255.255 UH      ppp0
> 0.0.0.0         210.50.118.58   0.0.0.0         UG      ppp0
> 192.168.0.0     0.0.0.0         255.255.255.0   U       eth0
> 192.168.0.0     0.0.0.0         255.255.255.0   U       eth1
>
> I want to connect two PCs to the 3rd gateway PC.

So this is the 3rd computer? And you want the following setup?:

Computer0 eth0 <-> eth0 Gateway PC ppp0 <-> ISP
Computer1 eth0 <-> eth1    ''

And you don't want to use a hub/switch for the internal network, right?
So then you'll have to use different address spaces for eth0 and eth1, 
otherwise it will use the first one even if the desired computer is on 
another interface. It might be possible to have the addresses in the 
same space by specifying more rules (eg. 192.168.0.2/32 on eth0, 
192.168.0.3 on eth1) but I don't see why it would be worth the extra 
work. If you have simple address spaces, you won't have to touch the 
routing table.
One computer could be 192.168.0.2, the other 192.168.1.2. The gateway 
would then be for example 192.168.0.1 and .1.1.

I see the first part of my answer wasn't really what you were looking 
for, but just in case...

hth,
/johan

--
Johan Ehnberg
johan@ehnberg.net
"Windows? No... I don't think so."