Ethernet bridging weirdness

[Douglas Stanley]

On Tue, Sep 14, 2010 at 3:57 PM, Serge E. Hallyn
<serge.hallyn at canonical.com> wrote:
> Quoting Douglas Stanley (douglas.m.stanley at gmail.com):
>> Hello all,
>>
>> I'm about at my wit's end, and I really hope some one might be able to
>> shed some light on this topic for me.
>>
>> I have two physically identical servers, both running 10.04.1, both
>> are completely up to date. Both are set up to be kvm hosts. On both
>> machines, I have an IDENTICAL /etc/network/interfaces, the only
>> difference being two lines where ip addresses are specified.
>>
>> The problem is, that both machines need a bridge set up on boot, so
>> that virtual machines can access it. One machine works 100% fine, the
>> other, the second bridge never comes up!
>>
>> My /etc/network/interfaces file can be seen at:
>> http://gist.github.com/579592
>>
>> Also, I just did a fresh re-install of 10.04.1, and performed the
>> updates on the machine that isn't working, thinking that maybe I did
>> something slightly different during the initial install. But it still
>> doesn't work.
>>
>> If I type:
>> sudo ifup br1
>> I get: "ifup: interface br1 already configured". But, ifconfig doesn't
>> list either my eth2 or my br1 devices. Also, brctl show doesn't list
>> my second bridge. But, if I edit /var/run/network/ifstate and remove
>> the br1=br1 line, then run "sudo ifup br1", it comes up just fine.
>> Similarly, if I "sudo ifdown br1;sudo ifup br1" that also works.
>
> Well br1 is manual, without a specified address.  As opposed to br0
> which is static with an address.  So I wouldn't expect it to show up
> with ifconfig.  Does it not show up with 'ifconfig -a' or 'brctl show'?
> Can you not specify an address for it (either using ifconfig or with
> dhclient)?
>

True, it is manual, but it's a bridge. I can't seem to find it now,
but that's precisely how it was supposed to be configured, according
to the documentation I was going by (I think it was one of the KVM
oriented guides). And, no, it's not showing up when I do a brctl show
on this one server (it shows up fine on the other *identical* server).

>> Any idea why it isn't coming up automatically on boot, when my other
>
> Because 'manual' means 'unconfigured', different from 'static' which
> means manually pre-configured.
>

But the other server with identical hardware, and identical config,
and identical interfaces file (except for 2 lines where ip addresses
are specified), works differently. On that box, the bridge shows up
fine using brctl show.

Thanks,
Doug

>> identical machine does just fine? Or even where I might look to try
>> and figure it out myself? There are no error messages in any of the
>> log files that I could find. I'm truly stumped!
>>
>> Thanks,
>> Doug
>>
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>



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