Funtion App routed through vnet NATGateway not using static outbound IP

Question

Hi,

I'm building a function app in azure and for whitelisting purposes I need to ensure a static outbound IP.
I have setup a vnet with a NAT-Gateway containing a static public IP, however when i check the list of outbound IP addresses in my function app is my static ip + several other addresses belonging to the serverfarm.
When I test my function app, the ip used is never the static ip i created.

How do I force all traffic through my static ip?

Best regards,

Tom

Answer 1

Did you try to add an application setting WEBSITE_VNET_ROUTE_ALL set to a value of 1?
This setting forces outbound traffic through the virtual network and associated NAT gateway.
Without this setting, internet traffic isn't routed through the integrated virtual network, and you'll see the same outbound IPs.

https://learn.microsoft.com/en-us/azure/azure-functions/functions-how-to-use-nat-gateway

Answer 2

Hi,

Can you make sure that you are forcing all outbound traffic of function app to the vnet as mentioned in the below doc ?

https://learn.microsoft.com/en-us/azure/azure-functions/functions-how-to-use-nat-gateway#update-function-configuration

Regards,
Karthik Srinivas

Answer 3

Update, the code I was using to check the outbound ip got the ip from a header in the http call, this somehow gave me other ip's than a python ip api.
Using that api, it did return my static ip, so i assume it was a problem in the code.

Thanks for the responses!