Hi,

I am trying to setup networking for a CentOS based KVM virtualisation environment on the host (I will ultimately be using OpenNebula to manage this environment). I've been allocated 1 fixed IP address for the main server and a /29 subnet (6 usable IPs) by my hosting provider hetzner.de. Unfortunately their documentation on this is not very clear - it describes setting up a bridged network in detail, but only casually refers to a routed approach being preferred - which I later find out is mandatory with a subnet from their customer support. All other how-tos I can find describe a bridged set-up (including the OpenNebula documentation). Trying any of these results in the server becoming unreachable.

Another point I'm confused about: trying to configure this through webmin (to help prevent any misconfigurations by my hand), I cannot create a bridged device unless the main interface (eth0) has the IP removed. As far as I understand, the main IP Address must be allocated to that interface to allow for routing... right? in which case, how would I configure a bridge device to route to, if these constraints are accurate?

So, ultimately, how do I configure a server with a single NIC (eth0) for routed networking using a bridge device (br0) with a /29 subnet? Or is hetzner incorrect in their assertion that I must use routing?

Thanks for your help,
Damian

OK, I think I managed to figure this out - seems the webmin interface was confusing me a little - I was trying to attach the bridhe device (br0) to the eth0 device, whereas I don't think this should be done for a routed approach. I then created a route to the subnet on br0 with the main eth0 ip address as the gateway and it seems that things are working ok from an initial set of pings etc.

Unfortunately, installing OpenNebula then trashed this configuration, and seems to want to force a bridged set-up.... I may be back with another thread if I can't figure it out :-(