[TriLUG] Networking and Fedora

[Justis Peters]

I researched this further and found that we need to also do the following:
+ take any IP addresses that are assigned to eth0 and move them to br0
+ copy the MAC address of eth0 to br0

I'm still trying to determine if we need to put eth0 into "promiscuous
mode".

By the way, how did you initially decide on how to setup the bridge and
routing tables? Did some tool do it automatically? Was there a tutorial
you were following?

Kind regards,
Justis

Joseph Tate wrote:
> Well, that went poorly.
>
> As soon as I issued the brctl command my whole network went dark.  The
> shell I was working in hung, and I forcefully disconnected to the top
> level ssh shell instead of the sub shell.  Now I can't connect to that
> host machine, or even the other machine that I was using to connect
> through it.  I guess it'll have to wait until I get home to fix it up.
>  That'll teach me to troubleshoot network issues remotely... :/
>
> On Wed, May 26, 2010 at 2:50 PM, Justis Peters <jtrilug at indythinker.com> wrote:
>   
>> Jeff Schornick wrote:
>>     
>>> Preparing to make a fool of myself...
>>>
>>>       
>>>> 10.2.2.0        0.0.0.0         255.255.255.0   U     0      0        0 eth0
>>>> 10.2.2.0        0.0.0.0         255.255.255.0   U     0      0        0 br0
>>>>
>>>>         
>>> You appear to have two routes to the same destination subnet, equal
>>> metric to two different interfaces.  Since eth0 and br0 aren't
>>> currently bridged, I'd imagine this would lead to rather inconstant
>>> delivery.  I'm honestly not sure how the kernel choses which route to
>>> use under these circumstances, but I'm 99% sure it won't deliver each
>>> packet to both.
>>>
>>> Do you perhaps want eth0 part of the br0 bridge group?
>>>
>>>       
>> Didn't see your reply before I sent mine. I think you've got it nailed,
>> Jeff. I hadn't noticed that eth0 is not yet attached to br0.
>>
>> The way that Xen users frequently do this is to rename the "real" eth0
>> to peth0 and then name the bridge itself eth0. You would then add peth0
>> to the bridge, along with all the virtual interfaces for the guest VMs.
>> Some people find this confusing; others like it.
>>
>> Joseph: The quick way to test our theory would be to remove the second
>> route and then add eth0 to the br0 bridge. The commands should look
>> something like this:
>>  route del -net 10.2.2.0/24 br0
>>  brctl addif br0 eth0
>>
>> I'm not sure of the preferred way to make those changes persistent in
>> Fedora, but I'm sure the answer is online and easy to find. Also note
>> that you probably want to run them in the order listed above. I suspect
>> that reversing the order might create a feedback loop between the
>> routing table and the bridge.
>>
>> Best of luck and let us know how it goes.
>>
>> Kind regards,
>> Justis
>> --
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>>
>>     
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