Summary

Auto route injection:
- provides non-disruptive fallback
- provides load splitting
- scalable wrt routing
  - reduces the overhead due to multi-homed sites
  - auto-route injection with tunnels eliminates routing overhead due to multi-homed sides
- little (none) inter-provider coordination
Auto route injection + NATs:
- allows to avoid renumbering
- enables to provide more control over load balancing