Re: Second ethernet card seems to cause networking failure?

[Matthias Feichtinger <asdf@vienna.at>]

On Fri, May 22, 2009 at 09:25:29AM -0700, Frank Miles wrote:

I recently added a second networking card to a hardware-test PC.  This elderly 
machine had been working reasonably well.  The second networking card is for 
eth1, etc., and /sbin/ifconfig shows things as properly connected, with eth0 
being the outside interface and eth1 being an internal 192.168.x.x interface 
for some special internal systems that have absolutely no need to communicate 
with the outside world, just this one PC.

The weird thing is that with normal booting configuration, pinging INet 
addresses fails.  This seems to be related to the order in which the 
interfaces come up: doing
        ifdown eth1 ; ifdown eth1 ; ifup eth0; ifup eth1
causes pings to fail; but if eth0/eth1 are reversed (bringing up eth0 last), 
or eth1 is simply suppressed, pinging URLs works (i.e. ping www.debian.org).

Regrettably this last does not entirely solve things - for example, I cannot 
do system updates: "apt-get update" fails to connect.

Eventually, if I play around long enough (killing eth1, killing my firewall - 
which hasn't changed since before adding the second NIC,...) I can do a 
system update but it's not entirely clear what the critical steps were to get 
that working.

I freely admit that I'm a hardware guy - I don't know much about networking.
Does anyone have a suggestion on where I might look to get this working 
properly?
Without sacrificing eth1?  Or at least some better diagnostic[s] to track down
where packets are getting lost?

TIA!
Version 4
As you are suggested to show /etc/network/interfaces there isn't really a need 
for, as long as you start /etc/ini.d/networking after any changes and 
controll it with ifconfig -a. The last one isn't really necessary.
I disabled any thingy of avahi, because there isn't any need for it
(/etc/default/avahi-daemon, /etc/network/if-up.d/avahi-autoip and
/etc/network/if-up.d/avahi-autoip changed from 755 to 644 by chmod
and avahi-daemon -k)
Then go on for routing - this should be fine now, IP-Masquerade-HOWTO if you 
like. 
Networking is fine with 3, I don't know anything with 5.

-- 
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Matthias:-)
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