I am working on a design for a large ISP. The idea is to split the ISP into 3 regions, each region has it own set of Reflectors wich in turn mesh with the ones in the other regions, then PEs in each region peer with the local reflectors....so far no challenge yet.
Now, each region has its own peering or ASBR routers for Transit peering, and obviously each area shoudl prefer it's own ASBR as 1st choice. this can be acheived by:
1-Loads of attributes manipulation, filtering between RRs of each region...and later adminsitration.
2-Leave attributes unchanged (except NH self), then path selection will be down to NH IGP metric. this will work fine until for one reason or the other metric are tampered with.
3-Combine ASBR and reflector functionality into one device, which is not desirable.
Are there any other options to suggest ?