We deploy a vmx100 in Azure vnet1 with site-to-site VPN between our locations. We also create a Azure vnet2 with vnet-to-vnet connection to vnet1. Is it possible to route our on-premise traffic to vnet2 through vmx100 in vnet1?
Create a route table in VNET2 that points to your vMX's IP with the appropriate subnets configured. Make sure your on-prem router knows to route the VNET2 subnet through the VPN tunnel and make sure you have the VNET2 subnet configured on the vMX.
Finally Azure allow peering between different subscription and I can implement my desired routing easy by vnet peering.
I followed the instruction below to set up peering between different subscription and create a routing table attached to vnetB to direct traffic to vmx100 in vnetA. I also defined vnetB subnet in vmx100 site2site vpn setting as one of the local network.