Thanks for everyone's reply.  I figured it out!  Whoo!  I can finally 
sleep. :)

For the curious...

A vanilla Ubuntu 7.10 Server install does not include NetworkManager or 
avahi, nor does it restrict any access via IP tables.  But it does 
install IPv6, but that was half the problem.  To disable IPv6, simply 
add the following to the end of the file "/etc/modprobe.d/blacklist", 
then reboot:

    install ipv6 /bin/true

That fixed the problem in one of my servers.

The other server took a while to fix because it has an Asus A8N-SLI 
Deluxe motherboard that does not like D-Link gigabit cards.  Lucky for 
me I have a stash of Linksys gigabit cards that work just fine.  It also 
didn't help having bad wiring and cables.  You'd think trying 3 
different patch cables was sufficient, but I guess not.  I didn't have 
to touch any routes or ARP address mappings.  Just remember, just 
because you can see a NIC, get it's MAC address, assign it an IP, ping 
it, doesn't mean that NIC actually works properly.

As far as the whole primary NIC thing is concerned, from what I can 
tell, when you install Ubuntu, it asks which NIC you want to be 
primary.  All this does is adds the entry for the NIC in the 
/etc/network/interfaces.  After installation, I don't think there is a 
concept of a primary NIC.

To change which NIC is eth0, eth1, etc, versions before 7.10 used the 
file /etc/iftab, but 7.10 uses "udev".  The ethX are tied to the MAC 
addresses defined in the /etc/udev/rules.d/70-persistent-net.rules file.

-Chris


Florin Iucha wrote:
> On Fri, Mar 21, 2008 at 10:53:24PM -0500, Chris Barber wrote:
> [snip]
>   
>> The problem is eth1 for some reason is whack on both machines.  I can't 
>> ping my public gateway or the other server over its public interface.
>>     
> [snip]
>   
>> Does Ubuntu/Debian identify one of the cards as the "primary" 
>> somewhere?  How/where does it tie a particular NIC to ethX?  Does 
>> anybody have any suggestions that I could try?
>>
>> I appreciate any help.  Thanks!
>>     
>
> Chris,
>
> Try disabling the 'magic' services: 'NetworkManager', 'avahi'.  Maybe
> even 'hal' and 'dbus'.  Ubuntu is trying to be overly protective of
> newbies with desktops - and it works, if you have one NIC with a
> dynamic IP address.  When you go out of the norm, it's better to take
> the matter into your own hands.
>
> Cheers,
> florin
>
>   
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>
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