FortiGate GRE Tunnel with Dynamically obtain IP source Interface

[most_ahdy]

Dears,

        I need to establish a GRE tunnel from Fortigate device, but the issue here is that the source interface WWAN interface with 3G/4G sim card which obtain its IP dynmically from the service provider.

When creating GRE tunnel interface using the command "config system gre-tunnel", it must has an IP address with local gateway parameter. and give me this error, if I try to ignore the local gateway parameter:

invalid gateway address!
node_check_object fail! for local-gw 0.0.0.0
Attribute 'local-gw' value '0.0.0.0' checking fail -61
Command fail. Return code 1

[hbac]

Hi @most_ahdy,

Unfortunately, you need to specify the local-gw and remote-gw IP addresses. Those values are required. 

Regards, 

[most_ahdy]

thanks @hbac ,  so we will not be able to configure GRE tunnel over WWAN, I Cisco I can use the tunnel source to be the physical interface it self, and destination to be the remote device