Please help, I can't find this anywhere How do I allow a specific IP from the internet + an internal IP port on the er605 that can be used in the local network? I've been looking everywhere and I can'

Good morning from the not so sunny UK! We have several ER7206 (and a few ER605) based at different clients sites, and we would like to have the ability to add 2 factor authentication to the VPN setup