DD-WRT PPTP Server
The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. It allows you to connect securely from a remote location (such as your home) to an LAN (Local Area Network) located in another location, such as your workplace, business office, etc. This way you can use the services provided in your office at the comfort of your home.
Set to Enabled
It is better to disable this option
It forces clients to use encryption, if it is disabled encryption can still be used but it will not be enforced. I suggest to enable it for security.
DNS1 & DNS2
DNS configuration, can be left empty.
WINS1 & WINS2
WINS configuration, can be left empty.
MTU & MRU
Both values should be the same. The default values are fine when the router is connected via ethernet but might need to be lowered in case of using another connection type.
Set it to a valid and not used local IP address.
Set it to the first of a continuous range of valid and not used local IP addresses. This range should be as wide as the number of Max Associated Clients.
Max Associated Clients
Maximum allowed simultaneous client connections.
Use CHAP Secrets unless you know what is RADIUS and want to use it.
In this box user names and associated password for the PPTP connection are written in plain text.