VNET peering performance?

Question

With VNET peering feature, I can peer a ARM VNET with a classic VNET to allow a Cloud Service web/worker role accessing the private IP of VMs hosted in the ARM VNET.

Per the document https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview

One benefit of VNET peering is low-latency and high-bandwidth connection between resources in different VNETS.

I am wondering how VNET peering performance compared with traffic within same VNET? I guess there is difference, but should be no big difference.

I know I can do performance testing to verify, but just want to have a general understanding of the VNET peering performance.

Answer 1

Based on my knowledge, they should be same.

After two VNets are peered, VMs or Cloud Services roles in the VNet can directly connect with other resources connected to the peered VNet. The two VNets have full IP-level connectivity. More information please refer to this link.

Also, you could refer to this blog. According to the author's result: Testing between VM’s in directly peered VNets showed no noticeable difference.

Answer 2

The performance should be roughly equal to the performance inside the same VNet, as VNet peering is not possible across regions, traffic goes through Azure Backbone, pretty much like in the same VNet scenario