I appreciate your input, I have 4 sites that are going to be connecting with dark fiber -see attached diagram- all 6500's with 10GB xenpaks, my question is: should all interfaces on the 6500'S be on the same network or should I have /30 networks between each site to site connection. Also, if you note from the diagram, should I place a patch cable to bridge sites A and C together bypassing site B? if I do that then I won't be able to use the /30 and would need a larger subnet or put them all interfaces on the same network...I hope this makes sense, I'm also assuming Layer 3 between sites is the way to go instead of Layer 2, what is the best approach from a IP design perspective? Thanks again.
Okay, didn't realise you had run out if 10Gb interfaces.
Only thing i can suggest is if you have a 1Gbps interface on both switches you could interconnect A & C that way and the routing protocol would only use this as a backup if the other links failed. But as i say you do have redundant paths anyway.