Following repository contains Packer template for creating Compute Engine image with BIND based DNS forwarder. Image is based on Centos 8 Linux OS.
Primary use case for custom DNS forwarder is situation when using Cloud DNS forwarding zones to forward DNS request towards target servers is not possible.
Example of such situation is hybrid cloud scenario in which there is on-premisses DNS server. In this scenario it is required to resolve on-premisses hostnames from GCP VPCs (using on-premisses DNS server).
Normally such requirement can be satisfied with Cloud DNS forwarding zones. However lets assume situation that connectivity from public ip range 35.199.192.0/19, used by CloudDNS as a source of forwarded DNS requests, is not allowed towards on-premisses network. It is required that all originating connections should use RFC 1918 address space instead.