Configuring Azure Route Server (BGP)

Azure route server uses BGP as an alternative to relying on just static routes. It populates BGP routes when enabled allow for dynamic route table population when combined with an NVA, Expressroute or VPN gateway.

Azure will default to routing with the longest prefix match. If the Azure route table shows 172.16.0.0 /16 and a route for 172.16.1.0/24 for traffic going to 172.16.1.6, Azure will choose the 172.16.1.0/24 route.

The order of precedence Azure routes are taken if route prefix are identical:

User defined routes > BGP routes > System routes. Azure system routes override BGP only for vnet, service endpoints, or vnet peering next hops.

If Azure route table detects two equal routes via NVAs it will enable ECMP (equal cost multi pathing) and can support BGP failover for high availability.