Xen. KVM, network bridging and multiple nics

[Stephen Spencer]

On Wed, Mar 7, 2012 at 5:54 PM, Jack <quiet_celt at yahoo.com> wrote:

> Objective: I'm installing XEN on a server I'm building. The server has two
> NICs, and will have a dual connection to the Internet, with 5 fixed used IP
> addresses. I plan to run 3 guests. One of those guests will use two IPs ,
> hopefully.
>
> Reading the KVM documentation (I'm also considering KVM, if XEN doesn't
> work out) and the XEN documentation leaves me a bit confused on the network
> bridging.
>
> The XEN documentation seems to indicate you NEED to have two NICs to do
> this. The KVM documentation seems to indicate you need to bridge in order
> for the guests to be network visible. But what I want to do is make sure
> that either one or both NICs are visible to any given guest.
>
> So can I bridge, both NICs independently? Or merge them into one fatter
> pipe? Or something else.
>
> Thanks,
> Jack
>
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Any documentation that indicates that you can't run a bridge on a system
with one NIC is, well, wrong.  The key is that you need to put your IP
address on the bridge interface.

So something like:

brctl addbr br0
brctl addif br0 eth0

ip address delete [inet address from eth0]/32 dev eth0

ifconfig br0 [inet address from eth0]

Then utilize the br0 interface in the vif stanza and you're in business.

Some folks seem to think its necessary for the bridge setup/tear-down be in
/etc/xen/scripts.  I prefer to use the OS network configuration gadgetry
myself, but I suppose inserting it into the xen network script
infrastructure makes it more distro/portable.

-- 
You know, I used to think it was awful that life was so unfair. Then I
thought, wouldn't it be much worse if life were fair, and all the terrible
things that happen to us come because we actually deserve them? So, now I
take great comfort in the general hostility and unfairness of the universe.
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