Summary

• Build a resilient Layer-2 network.

• Layer an IGP on top of it.

• Layer IBGP on top of that (perl is your friend).

• Layer EBGP on top of that (auto-generate configs from RPSL).

• Build routing policy using route-maps assigned to BGP sessions.

• Where availability really, really matters use HSRP.

• Result: You can withstand a huge variety of internal and external failures without loss of connectivity to anything.