[clug] Network bridges behind wireless ethernet bridges

Edward C. Lang edlang at edlang.org
Fri Dec 16 23:31:08 MST 2011


I'm a little puzzled by a problem I've run into this afternoon in the
process of setting up some a new computer and some virtual servers. I'm
using Ubuntu, KVM and QEMU to host a few Linux VMs on a system that sits
behind a wifi router in wireless ethernet bridge mode, which in turn
connects to my main wifi router.

PC <--> wifi router <--> wireless ethernet bridge <--> KVM host <--> VMs

I noticed that once I'd configured the bridged network connection on the
KVM host, my connection to it from my PC kept dropping out. My
connection to the VMs was fine. As soon as I connected the KVM host to
the main wifi router / switch, the problem went away.

I searched far and wide for similar issues, mostly finding Ubuntu bug
reports regarding the host network bridge interfering with the guests'
network, or manipulation of the guests' state interfering with the
host's network. Nothing I found spoke about only the host's network.

I'm beginning to suspect it's due to the double duplication of MAC
addreses: from my PC's perspective, everything behind the wifi bridge
shared the same MAC address; and then the host's network bridge again
reused the physical MAC address. Is that correct? Or am I wrong on that
assumption? I know little about this sort of networking and perhaps
stacking network bridges is well known to be silly...

I'd really prefer the KVM host to be wireless connected in some form or
another, and readily accessible by devices connected to the main wifi
router. Are there any PCIe wifi adapters that will bridge easily?

I wish pulling cat5/cat6 was an option but it's not.



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