TOI Author :: Dongliang Feng

When a core router has competing advertisements for the same prefix from various PEs, the local edge route should be selected as the best path based on the IGP metric of the resolving routes of those competing advertisements. Without the support mentioned in this TOI, when a BGP route has two or more levels of recursion, the BGP process does not utilize the IGP distance in the route selection process. 

This is achieved by using the next-hop of the static route as the peer IP address for the BFD session. The static route is either installed or removed based on the status of the underlying BFD session. A static route whose next-hop is configured to be tracked by BFD is referred to as a ‘BFD tracked static route’ in the context of this document. This feature is supported for both IPv4 and IPv6 static routes.

When a Provider Edge (PE) device loses BGP connectivity to the core (uplink) devices, it may be unable to forward any traffic from its downlink devices, typically CE (Customer Edge) devices. It is beneficial to indicate this connectivity loss to these CE devices so that they may find alternative paths to forward traffic.