[ovirt-users] vlan-tagging on non-tagged network

Felix Pepinghege pepinghege at ira.uka.de
Mon Jun 15 08:33:39 UTC 2015


Hi everybody!

I am experiencing a behaviour of ovirt, of which I don't know whether it 
is expected or not. My setup is as follows:
A virtual machine has a logical network attached to it, which is 
configured without vlan-tagging and listens to the name 'trunk'.
The VM is running an openvpn server. It is a patched openvpn version, 
including vlan-tagging. That is, openvpn clients get a vlan tag. This 
should not really be an issue but should satisfy the "why do you want to 
do it in the first place"-questions.
Anyhow, effectively, the VM simply puts vlan-tagged ethernet-frames on 
the virtual network. These frames, however, never make it to the host's 
network bridge, which represents the logical network.
My observations are: According to tcpdump, the vlan-tagged packages 
arrive at the "eth1"-interface inside the VM (which *is* the correct 
interface). Again, according to tcpdump, these packages never arrive at 
the corresponding network-bridge (i.e., the interface 'trunk') on the host.
I know that the setup itself is feasible with KVM---I have it working on 
a proxmox-machine. Therefore, my conclusion is, that ovirt doesn't like 
vlan-tagged ethernet-frames on non-tagged logical networks, and somehow 
filters them out, though I don't really see on what "level" that would 
happen (Handling the ethernet frames should be a concern of 
KVM/QEMU/Linux only, once ovirt has started the VM).
So this problem could be a CentOS issue, but I really don't see why 
CentOS should act differently than debian does (proxmox is debian-based).
Is this a known/wanted/expected behaviour of ovirt, and can I somehow 
prevent or elude it?

Any help is much appreciated! Of course I am happy to provide more 
information if that helps helping me :)

Regards,
Felix



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