Subject: Re: [vserver] Static Route on Loopback
From: Gordan Bobic <gordan@bobich.net>
Date: Fri, 15 Oct 2010 08:02:58 +0100

Adrian Reyer wrote:
> Hi Gordon,
> 
> On Thu, Oct 14, 2010 at 10:22:15PM +0100, Gordan Bobic wrote:
>> Is there a way to add a static route to a VM on loopback?
> 
> You don't need to. As the guest has no network, it doens't need to
> route, either. The kernel has the network and does the routing.
> Do you experience any problems with this setup?

Yes I am seeing a problem with this setup.

Host A:
lo:192.168.0.1/32
eth0: 192.168.1.1/24

Host B:
lo:192.168.0.2/32
eth0: 192.168.1.2/24

When host A connects to 192.168.0.2, the connection looks like it came 
from 192.168.1.1, rather than 192.168.0.1. I don't want my app on host B 
binding on listening on 192.168.1.0/24 interface. I want the connection 
to be going via the internal loopback only. I also want to keep the 
iptables rules relatively sane and intuitive.

Normally, this would be implicit by the network scope, but since lo is 
different and setting 192.168.0.1/24 on it would make the local host 
respond on the entire range, I need an alternative solution that would 
work more sensibly. Would using a dummy network device work for this? Or 
is there a better way?

Gordan