Edegrouter VPN server behind Hub Two router

[#1]

Is it possible to connect from the WAN to my Edgerouter VPN server (L2TP) through the Hub Two router (using port forwarding, not bridge mode)?  I've forwarded UDP ports  500,1701, and 4500 but can't connect. There is no option to allow ESP protocol, which I assume is the problem. Any suggestions?

[#2]

@Tori  have you got nat-traversal enabled on the Edgerouter ?

I'm no expert but I believe that should enable NAT-T and therefore you should only need to forward UDP ports 500 & 4500

https://helpdesk.emscom.co.uk/helpdesk/knowledgebase.php?article=166

[#3]

Having read about NAT traversal it seems that ESP is encapsulated inside the UDP packets, so only need ports 500 and 4500 forwarding as you said, so the issue lies with my Edgerouter config.

Thanks for pointing me in the right direction.