Several ptmp OSPF sessions over a single interface

[Ruben Laban]

Hello,

I'm currently performing some experiments to find the "best" way to 
inter-connect a bunch of routers using a shared medium. A common 
scenario would be a set of 4 routers, for instance a pair of border 
routers and a pair of core routers. I'd like either a full-mesh or 
circle topology. Putting all nodes in a /29 isn't ideal because of the 
DR/BDR/etc stuff. I want all nodes and links to be treated equally.
Using point-to-multipoint sounds like a decent solution. I can configure 
several sessions on a single link without interference, up to the point 
where the circle is created. Like this:

A - B
|   |
D - C

However, if I try to add a link between A and C, things start to go not 
as expected. A already has 192.168.255.2/31 (towards B) and 
192.168.255.4/31 (towards D) configured. If I add 192.168.255.10/31 
(towards C) and 192.168.255.11/31 on C (towards A), A and C can't ping 
each other using those addresses. This is because A will announce 
192.168.255.10/32 throughout the area and thus "overriding" the 
192.168.255.10/31 route on C (traffic will would be sent to either B or 
D, and not directly to A).

What would be the cleanest solution for this?

Regards,
Ruben Laban