Hi all,

Firstly, I have no idea of what the proper networking terms for this should be, so I hope this crude illustration may help explain what I want to do:-

I run either Fedora 11 or Centos 5.

I have a machine connected to my standard dlink home router.


PC eth0(192.168.0.10) -> router(192.168.0.1),dhcp & gateway

How do I add another network subnet within the eth0 for VMs?

PC eth0(192.168.0.10) -> router(192.168.0.1)
br0(172.16.1.0/24) -> router(192.168.0.1)

I want to then add VMs into the new network(172.16.1.0/24), and make them accessible to other machines in my home lan as well.

Sorry for the 'vague'-ness. Quite the network noob i am.

well your choice of VM system will sort this out for you, you should have no need to worry about this yourself. If you're using Xen under CentOS 5 then you'll be given a virtual eth0 which bridges to peth0, your physical eth0 device, which also connects to a xenbr0 interface which puts the VM's on the same subnet as the machine itself. If you put VM's on a seperate internal network you then need to sort out routing on the rest of your network to hit those IP's via this host machine which is kinda sucky. Alternatively you can look to nat all VM's to the IP address of the physical machine, but that would only assist with the VM's getting out, not others getting in. So a bridge is preferable really.

If you use VirtualBox after 2.x (2.1?), VirtualBox running on the host does the bridging itself so no special bridge configuration is required.

Hi guys,

thanks for the info. But I was wondering, If I wanted to do such a configuration in linux, how would I configure it ?

Add a Bridge interface, some tun / tap drivers and iptables for routing ?

Yes, tun and tap. I did it for VirtualBox prior to version 2.x. There was way to much half-informed information on the Internet about how to do it -- my head span -- but the VirtualBox manual was very helpful. Notes attached.

Attached Files

tun and tap.pdf (66.7 KB, 21 views)