Technical Tip: BGP with AWS transit gateway

When configuring BGP with AWS transit gateway, it is required that the routes originate from an eBGP peer and should have next-hop-self configured. Otherwise, the routes will be dropped on AWS.

To achieve this, enable  'next-hop-self' on the FortiGate.

Run the following commands on FortiGate:

config router bgp

    config neighbor

     edit <neighbor>

         set next-hop-self enable

     next

 end

If redistributing routes via route-reflector, the following change should be made:

config router bgp

    config neighbor

     edit <neighbor>

        set route-reflector-client enable

        set next-hop-self-rr enable

     next

 end

After that, the route is advertising correctly on the AWS side.

Related documents:
AWS document 
Technical Tip: How to modify BGP next hop for route reflector peering