SSL or IPsec VPN as per the ISO standards

First of all, please specify the type of modem that you are using. Since you haven't specified any, I am assuming a generic explanation to the problem.

1. First of all, consult the user manual or the instruction manual of your router to see if it supports these functions.
2. If it supports, then open up the router page, normally its 192.168.1.1. If it asks for user and pass, enter admin in both fields.
3. When you enter into the home page, look for the SSL options.
4. Define the SSL parameters against each IP of the customer as per the ISO standards.
5. Once done, save the options and restart the router so that the changes take effect.
6. Similarly define any number of users with their IPs in the SSL and apply.