Using 2 NICS?

Robert Ross rross at mcs.anl.gov
Wed Oct 25 15:01:02 EDT 2000


Karl,

Is this behavior happening for both directions of traffic, or just one?
In other words, is outgoing traffic going out of only one interface, is
incoming traffic coming into only one interface, or are both of these
happening?

You can use tcpdump to discover this, as well as looking at the xmit and
receive counts from ifconfig.

I would look at your routing tables as well, both on the local machine and
on the clients.  And your arp tables to see if the problem is at that
level.

It sounds like a routing table issue.  You might want to put routes in to
explicitly use a specific eth device for certain clients.

Rob

On Wed, 25 Oct 2000, Karl Bellve wrote:

> 
> 
> Robert Ross wrote:
> > 
> > What do you mean "Linux is assigning both IPs to the first NIC"?
> > Something like:
> > 
> > # ifconfig eth0 192.168.1.1
> > # ifconfig eth1 192.168.1.2
> > 
> 
> Right, this is the way I set it up.
> 
> However, it appears that one of the NICs seems to be used for both IPs.
> I am not sure why this happens. I can disconnect NIC #2 and still ping
> both IPs. If I disconnect NIC #1 and connect NIC #2, I can no longer
> ping either IP. If I use ifconfig -a, it reports correctly. Each NIC has
> its own IP, MAC address, mask, interupt etc. I was told that Linux
> assigns both IPs to the first working NIC card (eth0) when the networks
> are the same.


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