Question

Your company runs a web tier across a VM Scale Set and a set of on-premises IIS servers reachable over an ExpressRoute private connection. You must front both groups with a single Azure Application Gateway v2 so requests can be distributed to either the cloud or on-premises servers. When configuring the backend pool for this deployment, which approach correctly targets both sets of servers?

Accepted Answer

Create one backend pool that combines the VM Scale Set reference and the on-premises servers added as IP addresses or FQDNs, then associate it with the routing rule.

Answer

Application Gateway backend pools can only contain resources within the same virtual network, so the on-premises servers must be migrated to Azure first.

Answer

Create two separate Application Gateways, one for the VM Scale Set and one for the on-premises IIS servers, because a pool cannot mix target types.

Answer

Add the on-premises servers to the backend pool using their public IP addresses only, since private IPs from on-premises are not routable to Application Gateway.