[support] home agent on dummy interface

[Jeff Napper]

On 23 feb 2009, at 18:46, Romain KUNTZ wrote:

> Hi Jeff,
>
> On 2009/02/23, at 17:43, Jeff Napper wrote:
>> Greetings, all. I have a newbie question on setting up a virtual  
>> home agent.
>
> Do you mean a Home Agent with a virtual home link?

Er, good question. My setup will appear strange. I have the HA on the  
dummy interface of the mobile node (yes, I realize this doesn't help  
much with mobility <grin>), and the MN on a normal eth interface. The  
idea is to have a local "spoofed" HA on the dummy interface. I also  
started an radvd on the dummy interface.

The dummy interface is started with a "modprobe dummy" command and is  
configured with the HA address. Perhaps this is the problem? Should  
the dummy0 interface have a different address on the same network  
prefix instead?

>
>> According to the NEMO Howto, the Home Agent can be placed on a  
>> dummy interface (or simply an alias on the lo interface I'd guess).
>
> Yes, the home link can be emulated with a dummy interface. Note  
> however that it does not work with the loopback interface.
>
>> However, when I set this up, the HA cannot send packets because the  
>> dummy intf. doesn't allow outgoing packets not addressed to itself.  
>> In fact, the error is EPERM for the sendmsg() call for sending the  
>> BA. Is there something I'm missing in the routing somewhere or is  
>> this just not possible anymore?
>
> First, BA are not supposed to be sent through the dummy interface,  
> they should be sent via the interface connected to the Internet, in  
> order to reach your mobile node located somewhere in your network.

Indeed, this appears to be the problem (assuming you don't think the  
setup is inherently flawed). The BA cannot be sent through the dummy  
interface although it is destined for the localhost because the HA is  
running on the MN! In my strange configuration, the mobile node isn't  
located out somewhere in the network, but is co-located with the HA  
(for reasons having to do with the research).

>
> Or did you mean RA? I've tested on a 2.6.22 kernel and I could send  
> RA (with radvd) over the dummy interface. What is your configuration  
> and how did you create your dummy interface?
>
> Regards,
> -- 
> Romain KUNTZ
> kuntz at lsiit.u-strasbg.fr
> LSIIT - Networks and Protocols Team
> http://clarinet.u-strasbg.fr/~kuntz/

Thanks again for your help!

Cheers,
Jeff Napper
VU-Amsterdam