Performance difference between Azure public load balancer and internal load balancer

Question

Say, I have a front-end cloud service or service fabric hosted in one VNET and have another back-end service hosted in another VNET in same region.

I am wondering whether there is performance (latency) difference if I deploy Internal or External load balancer in front of my back-end service?

In my understanding, there should be no difference, no matter what load balancer (internal or external) used, the traffic from my front-end service in another VNET will be routed into my back-end service within Azure backbone network, won't go to outer internet.

Am I right?

Answer 1

Azure Load Balancer's public and internal configurations have no forwarding performance difference. The foundation for the product is the same. And, yes, the flows will always be routed on Microsoft's network.

There is an important difference between a public configuration and an internal configuration: support for SNAT for outbound connections. Only public Azure Load Balancer configurations make SNAT available. This means a machine in the pool can reach a public VIP associated with the pool; this is not permitted in for internal Azure Load Balancer configurations. Please be sure to review Understanding outbound connections for details on outbound connection options in Azure.