Troubleshooting Tip: Error when unsetting Local Gateway 6 '-651 input value is invalid.' in GUI

When an IPSec tunnel has been configured with a local gateway 6 address, the issue '-651 input value is invalid' may be encountered when attempting to unset the configuration.

config vpn ipsec phase1-interface

    edit "VPN_Access"

        set type dynamic

        set interface "wan1"

        set ip-version 6

        set local-gw6 2001:1:1::101

        set peertype any

        set net-device disable

        set proposal aes128-sha256 aes256-sha256 aes128-sha1 aes256-sha1

        set dpd on-idle

        set psksecret ENC <PasswordMask>

        set dpd-retryinterval 60

    next

end

The local gateway 6 address can be unset in the CLI:

config vpn ipsec phase1-interface

    edit "VPN_Tunnel_Name"

        unset local-gw6

    next

end

For further investigation, open a ticket with the collected HTTPS debugs using the Fortinet Support Tool.