[plug] Suse 9.2 2 nics

[Craig Ringer]

On Fri, 2005-06-24 at 12:30 +0800, doodli wrote:
> Can 2 nics work at the same time in a Suse setup??
> Have 3 Computers and trying to get all talking but no go.

Yes, they will work fine. You do need to make sure you understand your
network layout and the assignment of addresses, though.

> Sweat has 2 nics 192.168.0.1 and 198.168.0.3 mask 255.255.255.0
> Blood nic is 192.168.0.4 mask 255.255.255.0
> Tears nic  is  192.168.0.2 mask 255.255.255.0    Has winxp but has no 
> trouble see sweat when plugged in.

This will not work well. It might end up working, but I certainly
wouldn't do things that way. Your computer will think that it can send a
packet out either eth0 or eth1 to reach either host because of your
address and netmask choices, but it can't.

There are two options to do it "right" - separate networks, or bridging.
Bridging might be simpler and cleaner, but might be trickier to get
going if SuSE doesn't provide easy-to-use tools to set it up.

I'm not including step-by-step instructions for these. I don't know SuSE
well, and don't know its graphical config tools at all. I'll let you
look up the details of how to set these things, or maybe someone with
SuSE on the list can help out.

SEPARATE NETWORKS
-----------------

You can build your network as two smaller networks - one that connects
Sweat to Blood and one that connects Sweat to Tears. Sweat could
optionally enable communication between them.

First, you'd assign 192.168.0.1 to eth0 and 192.168.1.1 to eth1, then
lay things out like this (will only be readable with fixed-width font):

           |------Sweat-----|
          eth0             eth1
      192.168.0.1      192.168.1.1
           |                |
           |                |
        Blood             Tears
     192.168.0.2       192.168.1.2

This will ensure that your SuSE box knows which host to send which
packets to reliably. You could use other network schemes if you wanted,
such as segmenting 192.168.0.0 into smaller bits using a
more-than-24-bit netmask, but the above is simpler and easier to
understand.

If you want 'Blood' to be able to talk to 'Tears' and vice versa (you
choose weird hostnames, by the way) you will need to tell Sweat to route
between eth0 and eth1. There is no need to do NAT ("IP masquerade")
between the two, simple routing will be fine and in fact higly
preferable.

BRIDGING
--------

If the above scheme doesn't appeal, you do have another option. You can
bridge eth0 and eth1 into a single virtual interface, then assign it a
single IP. This permits you to hand out addresses to hosts on the
network as if it was in fact one network segment instead of two smaller
ones. Your logical network would look like this:

            
                 Sweat
             br0(eth0,eth1)
              192.168.0.1
           |-------|--------|
           |                |
           |                |
        Blood             Tears
     192.168.0.2       192.168.0.3

even though physcially it'd still be wired as in the first diagram. This
would also let 'Blood' and 'Tears' talk to each other without fuss (so
long as your firewall permits it).

--
Craig Ringer