[CentOS-virt] proper bridging technoque

Digimer lists at alteeve.ca
Fri Nov 22 01:52:29 UTC 2013


It's not so much hard as it is knowing all the hops in your network. If
anything along the chain has a low MTU, the whole route is effectively
reduced.

On 21/11/13 20:20, Nico Kadel-Garcia wrote:
> This is int4eresting stuff. I do note that the "virt-manager" tool,
> and NetworkManager, give *no* insight and detailed management
> sufficient to resolve this stuff.  Note also that dancing through all
> the hoops to get this working, end-to-end, is one of the big reasons
> that most environments refuse to even *try* to use jumbo frames, as
> helpful as they sometimes are to heavy data transfers.
> 
> On Thu, Nov 21, 2013 at 6:58 PM, Digimer <lists at alteeve.ca> wrote:
>> On 21/11/13 18:20, aurfalien wrote:
>>>
>>> On Nov 21, 2013, at 2:45 PM, Digimer wrote:
>>>
>>>> The 'vnetX' number doesn't relate to the interface, bridge or anything
>>>> else. The vnetX number is a simple sequence that increments each time a
>>>> VM is started. So don't think that you need 'vnet6'... it can be anything.
>>>>
>>>> The 'brctl show' output from earlier showed that both vnet0 and vnet1
>>>> were connected to br0. You can try using the bridge utils to remove them
>>>> from br0 and connect them to br6 as a test.
>>>>
>>>> --
>>>> Digimer
>>>
>>> Well, when I remove vnet1 from br0 and add vnet1 to br1, I loose connectivity with my VMs.
>>>
>>> No biggy so I reboot my entire host.
>>>
>>> Then vnet1 show back under br0.
>>>
>>> I just don't understand enough about this to get a clue, depressing.
>>>
>>> - aurf
>>
>> Think of each bridge as if it were a physical switch.
>>
>> When you detached vnet1 from br0, you unplugged it from a switch. When
>> you attached it to br1, you plugged it into another switch.
>>
>> If there is no connection out to your network/internet on a given
>> switch, then anything plugged into that switch will go nowhere. Same
>> with bridges.
>>
>> You seemed to indicate earlier that the main connection was on br6. Is
>> this true? If so, then "switch" br6 is the switch with the "uplink" to
>> your network. Plug a VM into it and you can route out through it.
>>
>> When you rebooted the VM, the hypervisor read the definition file. That
>> definition file says to plug in the server to br0. So it makes sense
>> that the reboot reconnected it to br0.
>>
>> If you want to use jumbo frames on the br0 switch, you need to set the
>> larger MTU on the interfaces are all set to your desired MTU size.
>>
>> --
>> Digimer
>> Papers and Projects: https://alteeve.ca/w/
>> What if the cure for cancer is trapped in the mind of a person without
>> access to education?
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-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?


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