Subject: Re: [vserver] Static Route on Loopback
From: Gordan Bobic <gordan@bobich.net>
Date: Fri, 15 Oct 2010 11:21:44 +0100

I just confirmed that using dummy interfaces with a real netmask does 
actually make things work the way I want. I notice the lo /32 interface 
still gets created with the same IP. Are there any drawbacks in doing it 
this way?

Gordan

Gordan Bobic wrote:
> 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