App Services per instance allows for 128 SNAT. My question is that would an App Service Environment v3 using isolated plans still be limited to 128 ports per instance or because it is isolated, would it I get the full 65k per instance?
If there is supporting documentation that I have missed that provides this information, please include it.
As mentioned in this documentation, Azure uses source network address translation (SNAT) and Load Balancers (not exposed to customers) to communicate with public IP addresses. Each instance on Azure App service is initially given a pre-allocated number of 128 SNAT ports.
ASE adheres to IaaS limitations, therefore port limits are based on your VM pool size.
For more Information, you can refer this SNAT for outbound connections documentation
you are correct, an easy workaround is to integrate your app with a VNET and use a NAT GW, that gives you 65000 connections / IP and you can use up to 16 IP addresses in a prefix and if that is not enough you can deploy multiple NAT gateways as well
