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Re: 2 e1000 interfaces not working together

Hello George,

On 25.09.2006, at 18:29, George Borisov wrote:

udo waechter wrote:

As long as I ifup one of the two interfaces everything is fine. Not
everything though, since both IP Adresses are reachable. there is no
other computer having one of the two IPs, since none of them are
reachable as soon as I ifdown the interface. This is the first strange

I'm not sure what you mean here.
If only one Interface is up (no matter which one) I can not only reach the IP adress of that interface but also the other IP Adress which is not assigned to any computer in the subnet. It also works vice-versa. When both cards are down, none of the two IPs are reachable (via ping or ssh or so)

The second strange thing is, that the computer can not communicate with
the network as soon as both interfaces are ifup'd
Both IP-Adresses are from the same subnet, have the same subnetmask and
the same gatewway.

This is not a good idea. By having 2 different interfaces on the
same subnet you are creating 2 different routes to this subnet.
You should definitely only have one default gateway (unless you
are doing split-routing, or something).
Yes, that was also my thinking when we got the first machine with two interfaces. The solution that we have no is to assign each of the interfaces a different subdomain and then make all the clients for our co-workers usee one domain, and all computers which are used by students use the other sub-domain. Having this a route for each of the interfaces, things are ok again, or aren't they? As I understand it, traffic coming in on eth0 is recognized by the kernel as such and it knows that an answer has to be sent via eth0. or is this false?

What exactly is psplit-routing?

However, I am surprised that they both break, as I would have
expected one of them to continue working.
Me too, since this is not the first computer with this setup, all others work perfectly well.

If you must have both interfaces on the same subnet then I would
look into bonding (using the "ifenslave" package), or bridging
(using the "bridge-utils" package). Your choice would depend on
what your objective is.
I'll try the one or the other. Maybe it is a problem with the Intel Hardware. It does not like such setups, or so...

Hope this helps,
a little bit, thanks.

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