Network route discovery is facilitated by BGP.
EBGP is used to prevent the redistribution of routes that are in the same Autonomous System (AS) number as the host. It is also required to influence route selection on the branches with AS-Path prepending. EBGP multipath is enabled so that the hub FortiGate can dynamically discover multiple paths for networks that are advertised at the branches.
The neighbor range and group settings are configured to allow peering relationships to be established without defining each individual peer. Connecting branches have their tunnel interfaces configured within the range of the BGP peer.
In order to facilitate the fastest route failovers, configure the following timers to their lowest levels:
To configure BGP on the hub FortiGate:
config router bgp set as 65500 set router-id 10.10.0.1 set ebgp-multipath enable set graceful-restart enable config neighbor-group edit "branch-peers-1" set soft-reconfiguration enable set remote-as 65501 next edit "branch-peers-2" set soft-reconfiguration enable set remote-as 65501 next end config neighbor-range edit 1 set prefix 10.254.0.0 255.255.255.0 set neighbor-group "branch-peers-1" next edit 2 set prefix 10.254.1.0 255.255.255.0 set neighbor-group "branch-peers-2" next end config network edit 1 set prefix 10.200.1.0 255.255.255.0 next edit 2 set prefix 10.200.0.0 255.255.255.0 next edit 3 set prefix 10.200.3.0 255.255.255.0 next end end