On Tue, 2009-04-07 at 18:39 -0300, Klaus Heinrich Kiwi wrote:
I was thinking about the semantics I described above. It ultimately means that we'll have a bridge for each VLAN tag that crosses the trunk interface. So for example if guests A, B and C are all associated with VLAN ID 20, then:
eth0 -> eth0.20 -> br0 -> [tap0, tap1, tap2]
(where tap[0-3] are associated with guests A, B, C respectively)
Yes, I think that's how it should work; it would also mean that you'd first set up eth0 as a separate interface, and new bridge/vlan interface combos afterwards. AFAIK, for the bridge, only bootproto=none would make sense.
The things that concerns me the most are: 1) How scalable this really is
I don't know either ... we'll find out ;)
2) The semantics are really different from how physical, 802.1q-enabled switches would work.
Because (2) really creates new switches for each new VLAN tag, I wonder how management would be different from what we have today with physical switches (i.e., defining a port with a VLAN ID, assigning that port to a physical machine) - unless we hide it behind libvirt somehow.
The reason we are creating all those bridges isn't the VLAN's - it's that we want to share the same physical interface amongst several guests. And I don't know of another way to do that.
Are there other options? Since a tagged interface like eth0.20 is kind of a virtual interface itself, would it be appropriate to use those directly?
You can use it directly, I just don't know how else you would share it amongst VM's without a bridge. David