ExpressRoute outbound ECMP

• All testing done in West Europe region.
• All outputs show effective-routes from Spoke VM NIC

Single circuit (Primary/Secondary paths same AS-Path)

VNG

ECMP outbound over two links as expected.

Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.36
Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.37

VNG + ARS

ECMP broken outbound, single link used as per open documented bug here.

Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.36

VWAN + RI

ECMP outbound over two links - official support pending.

Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.36
Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.37

VWAN (New Hub October 2023)

ECMP outbound over two links - official support pending.

Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.36
Virtual network gateway, Active, 192.168.2.0/24, Virtual network gateway, 10.3.129.37

Dual circuits (4 paths, all same AS-Path)

VNG

ECMP outbound over four links as expected.

Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.2.146.56
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.2.146.57
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.20.88.55
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.20.88.56

VNG + ARS

ECMP broken outbound, single link used as per open documented bug here.

Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.2.146.56

Beyond 4 pathes (Beyond 2 circuits)

VNG

ECMP outbound over five links. Up to Azure SDN limit of 8 links (4 circuits) - link.

Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.2.146.56
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.2.146.57
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.20.88.110
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.20.88.55
Virtual network gateway, Active, 172.16.240.0/25, Virtual network gateway, 10.20.88.56