advice on OSPF design.

Define main sites to be area 0.

or make it all backbone - 16 or 17 routers is well within OSPF single area size limits.

this assumes that OSPF doesnt need to support lots of other routing - e.g. within some sites, or over another WAN.

the rule of thumb is that if part of your network has "different" characteristics then where those bits meet is a good place to put an area border - e.g. part of he network is fully resilient, one bit has relatively unstable links etc.

You could do worse than read the OSPF RFC - the intro bit goes on about what OSPF can do and sensible structure, although it isnt paranoid enough for me.

Also the SPF calculations dont happen between areas - so if you use 1 stub per branch you arent actually using the whole point of having OSPF....

Very simple answer. create router ospf 1 process on both main routers. put the network of the 2m links that connect the main sites in area 0. Use area 10 for the branches. put the point to point network for the connections to the branch offices in area 10. On the branch routers create router ospf 1. put the the point to point network for the connections to the main offices in area 10. put the network of the LAN in area 10, under ospf 1. show ip ospf nei, sh ip route, ping to test.

Thanks Guys, Specially datakazem, Same design was in my mind (with