Dial-Up Networking Call Back

Setting up a “Dial-In Connection” opens a door for “unwanted visitors”, which far too often manage to break in to systems. Setting up passwords gives only a limited protection, because unluckily, a lot of people choose easy-to-remember password (like: the of your wife/children or their birthday).
Security can be largely improved by implementing “Call Back“:
once the server has identified the caller, the connection is terminated, and then the server calls you back, re-establishing the connection.
On the RAS server, define for each user in the “Remote Access Admin“:

In addition of allowing a user to
“dial-in”, define the “Call Back”
option and preset the number,
allowing this user to connect
ONLY from this predefined

Setup of a Windows NT 4 Dial-Up Connection

Select from the “More“-button the “User Preferences:

You can enter here (optional) the number to be called back, but that would NOT give you the additional security, we have already defined a FIXED call-back number on the server.

we start our connection in the usual method by
dialing from the “Dial-Up Networking Client
to the “Remote Access Server”
Once the server “picks up the phone”, the
systems verify the “user-name” and “Password”.
The connection is then terminated, and the
“Dial-Up Networking Client” now waits for
the “Remote Access Server” to call back.
Within a few seconds, the return call come in.
The “username ” and “password” is verified
again, then the connection is finalized.
Then, you are connected.

Setup of a Windows95 Dial-Up Networking Client

When defining your connection from a Windows95 “Dial-Up Networking” Client, there is no possibility to define a Call-Back option.
However, the functionality is fully supported

You start your connection.
When the server “picks up the phone”,
the “user-name” and “password” is
verified, used to identify the caller.
You then get informed about the
“Possibility” for a “call-Back”.
However, if the Server enforces
a specific call-back number, you
can only go ahead: OK
The connection is terminated, and
your “Dial-Up Networking” Client
is now waiting for the call-back.
“User-name” and “Password” are
verified again.

You are now connected and can browse the system.

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