Force all outbound traffic from Azure Function trough Firewall

I assume that you have a HUB/Spoke design where there is a route table, that has a default route that points all traffic to the Firewall in the hub.

On the Function App you deploy in a spoke, you need to configure outbound network integration.

It is important to enable: “Outbound internet traffic”

The configuration on the Function App needs the setting: “vnetRouteAllEnabled” = 1