I have a GCP Classic VPN (Profile based routing) to an onsite end point. The tunnel is established and I can see that the appropriate routes are added to both GCP and the onsite router.
I have created Ingress and Egress Firewall rules at both ends w/ logging enabled and the GCP Connectivity Tests show that a packet from the default GCP network would reach the destination onsite LAN address.
Packet could be forwarded
Configuration analysis determines that the packet could be forwarded to VPN gateway (-)
I have a test App Script that attempts a URLFetch from an onsite server. I believe the GAS project is correctly associated with the GCP running the VPN connection but whenever I run the GAS project it fails with a "Bad Request" and no traffic is logged as being transferred over the tunnel.
Any ideas what I am missing?
TIA.