I was able to get this to work. This is what I did:
- Download GL-AR300M16 OpenWrt only 3.0 from GL.iNet download center
- Update firmware
- reset to factory default
- connect to 192.168.1.1
- set password
- change IP
- enable wireless
- connect internet (modem) to WAN
Go to System-Software
- update packages
- search for vpnc
install:
- vpnc
- vpnc-scripts
- luci-proto-vpnc
System-reboot
Network-interfaces: Add new interface…
name (4 charachters only! e.g. ‘TUN0’)
protocol: VPNC
VPN Server: enter url of server
Output Interafce: wan
MTU: 1380
Username: name as entered in FritzBox
Password: password for user on FritzBox
Auth Group: same as Username
Group Password: Preshared key as in FritzBox
IKE DH Group: dh2 (should be default)
Perfect Forward Secrecy: nopfs
DPD Idle Timeout: 0
Go to tab Advanced… Make sure ‘Bring up on boot’ is checked
Go to tab Firewall Settings… Assign to ‘LAN’ zone
Click ‘Save and Apply’
Network-interfaces:
Make sure TUN0 has an IP address and is up.
Now (from: Installing WireGuard on routers running OpenWrt and LuCI - Guides - AzireVPN):
Network-Firewall: Add…
Name ‘tun0zone’
Input: reject
check Masquerading
check MSS clamping
Covered networks: check ‘tun0’
Click ‘Save and Apply’
In zones ‘lan => wan’ click edit
In Inter-Zone Forwarding, in Allow forward to destination zones, leave ‘wan’ checked, and also check ‘tun0zone’
Click ‘Save and Apply’
Check if you can connect to equipment in other network and traffic gets routed through there.