Google_compute_ha_vpn_gateway doesn't let us explicitly mention ip addresses in vpn_interfaces {} block

Hi,

We setup a HA VPN via google console and it reserved 2 external gateway IPs for the tunnel interfaces. After establishing the connection to our office networks, I tried to script the tunnel and router using google_compute_ha_vpn_gateway. Everything worked except for the external IP addresses, google would not let me select which IPs I would want in my gateway, instead it would auto select every time.

I tried to find this information inside the official documentation (Terraform Registry) for this resource but there was nothing mentioned like this, under the vpn_interfaces {} block, there is an option to mention “ip_address” but it gives an error every time I do a terraform apply:

Error: Value for unconfigurable attribute

│ with module.m_vpn[0].google_compute_ha_vpn_gateway.vpn-ha-gateway[0],
│ on modules/m_vpn/main.tf line 11, in resource “google_compute_ha_vpn_gateway” “vpn-ha-gateway”:
│ 11: resource “google_compute_ha_vpn_gateway” “vpn-ha-gateway” {

│ Can’t configure a value for “vpn_interfaces.1.ip_address”: its value will be decided automatically based on the result of applying this configuration.

I spoke with google and they confirmed that google has not yet included Cloud VPN to their Bring Your Own IP feature, so there is no possible way we can select our own IPs. I think it should be mentioned somewhere in the documentation if it is not possible. Does anyone else faced the same issue?