BGP may be selected for scalability and is well suited for very large networks. BGP can be configured as External BGP (eBGP) to route between autonomous systems or Internal BGP (iBGP) to route within a single autonomous system.
Layer 3 leaf-spine networks use ECMP routing. eBGP and iBGP handle ECMP differently. By default, eBGP supports ECMP without any adjustments. To reduce configuration complexity, Dell Technologies recommends using eBGP in leaf-spine fabric deployments.
BGP tracks IP reachability to the peer remote address and the peer local address. Whenever either address becomes unreachable, BGP brings down the session with the peer. To ensure fast convergence with BGP, Dell Technologies recommends enabling Neighbor fall-over with BGP. Neighbor fall-over terminates BGP sessions of any directly adjacent peer if the link to reach the peer goes down without waiting for the hold-down timer to expire.
