Azure Virtual Wan site links

Question

Hi,

I am testing S2S Azure Virtual Wan, our on-premise site has 2 different internet connections that I would like to use for failover, so a main and a backup internet connection dedicated to the S2S vpn.

On premise I have simply chosen to use static routes with different metrics in order to manage the failover.

On Azure Virtual Wan I can configure multiple links for each site but I don't understand if they are aggregated by default or can be weighted.

How can I avoid Azure Virtual Wan to use the backup link as soon as the main is connected ?

Thanks

Answer 1

A site-to-site IPsec connection coming into a Virtual WAN’s VPN terminates on the VPN gateway instances inside a virtual hub. A site-to-site connection represents the connectivity between the VPN site and the Azure VPN gateway. It consists of one or more link connections. Each link connection consists of two tunnels with each tunnel terminating on a unique instance of the Azure Virtual WAN VPN gateway. Up to four link connections can be set up in the site-to-site connection, which makes it possible to have up to eight tunnels within a site-to-site connection. Azure supports up to 2000 tunnels terminating inside a single Virtual WAN VPN gateway.

Virtual HUB VPN uses ECMP (equal cost multi-path routing) across all terminating tunnels. So it sees all the routes as equal cost paths by default and divides the traffic equally between them from Azure to on-premise. However, it can be weighted between them if you use BGP for routing and use BGP parameters.

Branch devices that provide path selection can enable appropriate policy in the branch management solution to steer traffic across multiple links to Azure. For example, the ISP 1 link can be used for higher priority traffic and the ISP 2 link can be used as backup. So BGP parameters on-premise can be used for setting preference between the VWAN links and using this once the active connection comes up, it can be preferred. Hope this answers your questions. Thank you!

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