OK, so OSPF uses 100mb as a reference bandwidth by default and divides that by the interface bandwidth to create the cost for that route.
Is the reference bandwidth only locally significant to the local router, or is it globally significant.
So if I wanted to take into account the bandwidth for gig and 10 gig interfaces, can I change the reference bandwidth only on the devices with that type of interface or should I change it globally on all routers?
The value is locally significant, however best practice is to config the same value for autocost-ref-bandwidth across the board.
This will ensure that you dont get any funny routing issues, with some router choosing one path and another choosing a different return pth, ie asymetrical routing.