[Xorp-hackers] Recursive next-hop lookup..

[Kristian Larsson]

Pavlin Radoslavov wrote:
> Steffen Schumacher <steffen at schumacher.dk> wrote:
> 
>> Hi!
>>
>> I read the status page, so that the feature in subject still isnt
>> implemented. (http://www.xorp.org/status.html)
>>
>> Or is it simply not working? Does anyone know if it will be working
>> by 1.5?
>>
>> Currently I've used quagga, but it seems that it also doesn't support
>> it. I'd really like it, because my ISP will only announce a default
>> candidate via bgp, vs. a default. The idea is that I configure a static
>> default directed at this Default candidate, and my default will then
>> move around when my eBGP peers go up/down.
> 
> Could you please send an ASCII diagram with your topology and a
> little extra explanation, because we are finding it difficult to
> understand the issue you are facing.

The way I understand it..
One router on Steffans end with two connections, one to each ISP. (Hope 
my ASCII doesn't get mangled by this bloody email client).

+-------+     +-------+
| ISP-A |     | ISP-B |
+-------+     +-------+
        \      /
       +---------+
       | Steffan |
       +---------+

The "normal" way of doing this, provided that Steffan can't take a full 
table, would be for ISP-A and ISP-B to announce a default route each.
Another way, and this is the scenario at hand I believe, would be for 
ISP-[AB] to announce 1.3.3.7/32 (with the next-hop of ISP-[AB]'s router) 
and then you would point whatever route you want towards 1.3.3.7 which 
would be looked up recursively and resolve to ISP-[AB]'s next-hop.
Or if ISP-[AB] would announce different "default candidates" then you 
could perform some crude load balancing towards the different "default 
candidates" of ISP-[AB].


Regards,
   Kristian.