Ethernet bridging weirdness

[Douglas Stanley]

On Tue, Sep 14, 2010 at 5:19 PM, Scott Phelps <phelps.scottie at gmail.com> wrote:
>
> On Sep 14, 2010, at 4:39 PM, Douglas Stanley wrote:
>
>> 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.
>
>
>
> Try removing 'bridge_maxwait 0' from the config.  The bridge setup
> scripts will not wait for the bridge ports to enter a forwarding state
> if set to 0 and may be failing as a result.
>

Removed the bridge_maxwait 0 line, and still doesn't work.

Also, installed ethtool on both identical machines. On the one where
the bridge starts automatically, ethtool eth2 shows link detected:
yes. On the other machine, it shows no. BUT, if I sudo ifdown br1 &&
sudo ifup br1, then do ethtool eth2 again, it shows link detected:
yes.

I'm baffled, and getting quite frustrated. Anyone know if there's
anything I can do to debug? In syslog, on the machine where it works,
I seen eth2 being mentioned, then br1 being mentioned when it comes
up. On the machine where it's not working, there is no mention of eth2
OR br1.

Thanks,
Doug
> //Scott
>
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