IssueTracker

What you would like to accomplish:
-  Setup CPanel DNS server which is hosted in GCP VM instance and assign IP in custom name servers in CPanel environment

How this might work/ Problem encountered:
- Setup CPanel DNS server hosted in GCP VM instance and assign IP address in custom nameserver.
- Able to add virtual NIC in CPanel environment however the reserve internal VPC IP addresses assigned in virtual NIC is having an error of "Not routable" in CPanel environment which is hosted in GCP VM instance. See attach link screenshot for the CPanel error.

If applicable, reasons why alternative solutions are not sufficient:
- Deployed using GCP Marketplace CPanel & WHM, found "add interface" is grayed out and disabled.
- Add IP address in Cpanel environment and generated virtual NIC (i.e. eth0:cp1 and eth0:cp2). Then assigned reserve internal IP addresses. However upon CPanel validation, the assigned IP addresses are not routable. see attach screenshot and link [4] for procedure in deploying CPanel nameserver.
- Configured GCP NIC IP address routing policy [3] using virtual NIC assigned internal IP and gateway IP address, still unable to configure the virtual NIC. GCP routing policy justified Cpanel virtual NIC won't suffice in how Cloud VM instance multi NIC works and should add NIC not virtual NIC.
- Created CPanel VM instance Snapshot, create new CPanel VM using the Snapshot to add network interface and configure routing policy. However additional NICs is disconnecting outside the network after CPanel restarted and but not yet tested to assign the GCP VM NIC IPs in CPanel custom nameserver.

Other information (workarounds you have tried, documentation consulted, etc):
- Provided useful links [1-8] from GCP side in setting up routing policy, workaround in adding NIC and CPanel nameserver deployment
- Followed CPanel documentation from CPanel support in how to setup nameserver. See ​links [9-11]

Links:
[1]  https://blog.cpanel.com/how-to-create-your-own-name-servers/
[2] https://cloud.google.com/vpc/docs/create-use-multiple-interfaces#max-interfaces
[3] https://cloud.google.com/vpc/docs/create-use-multiple-interfaces#configuring_policy_routing
[4] https://docs.cpanel.net/knowledge-base/dns/how-to-set-up-nameservers-in-a-cpanel-environment/
[5] https://docs.cpanel.net/knowledge-base/accounts/from-whm-to-website/
[6] https://tickets.cpanel.net/
[7] https://manage2.cpanel.net/
[8] https://docs.cpanel.net/knowledge-base/cpanel-product/how-to-purchase-a-cpanel-license/
[9] https://docs.cpanel.net/knowledge-base/general-systems-administration/how-to-disable-network-manager/
[10] https://docs.cpanel.net/installation-guide/cpanel-dnsonly-installation/
[11] https://docs.cpanel.net/knowledge-base/general-systems-administration/1-1-nat