Archer C80 UDP port forward for ports 500 and 4500 not working
I've upgraded from TL-WRN1043ND to Archer C80, and suddenly my VPN which is hosted on a Raspberry Pi stopped working. Ports 500 and 4500 were the only ports that I forwarded on my old router, and everything was working smoothly. But with Archer C80, it doesn't work. Raspberry Pi has a statically assigned address from DHCP server of the router, and I can forward softethervpn's TCP port 5555 just fine, just not the two IPSEC/L2TP required UDP ports.
I'm aware that some Archer versions offer VPN, so is it possible that these ports are explicitly disabled by the firmware due to that fact? If so, how can i enable those ports to be used in port forwarding? UDP forwarding works, I've tried it with port 53, and did a "dig" command pointing to my public address and an internal dns hostname created by Samba AD server - it works.