[CentOS-virt] proper bridging technoque

Fri Nov 22 01:20:32 UTC 2013
Nico Kadel-Garcia <nkadel at gmail.com>

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/
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