A router can call back PPP
clients that dial in. As shown in the Figure, to configure PPP
callback for a server, perform the following steps (the following
step numbers correspond to the numbers in the Figure):
- Configure IP on the dial-in line.
- Use the dialer callback-secure
command to disconnect calls that are not properly configured for
callback. A callback server with dialer callback-secure configured
disconnects any unconfigured dial-in users.
- Set up dialer map with the dialer map
and dialer-group commands.
- Use the ppp callback accept
command to enable callback.
- Define the PPP authentication method with
the ppp authentication chap command.
- Configure dialer callback-server username
in a dialer map-class to identify the name in the dialer map as a
valid callback client. When callback client router dials in and is
authenticated, the call is disconnected. For example, in the
Figure, a return call is made to 555-5678, as configured by the dialer
map command. The dialer map command identifies the
map class to be used for this connection.
- Use the dialer hold-queue timeout
command to set the server hold-queue timer, which identifies
the number of seconds that a callback client or server holds
packets destined for the client while waiting for the return call
to be completed.
Use the dialer enable-timeout command
to determine the amount of time that the server waits before making
the return call.
PPP Callback-Additional Feature
from Cisco
Another command for callback is
dialer
callback-secure, which is a Cisco proprietary command. This
command ensures that the initial call is always disconnected at the
receiving end and that the return call is made only if the username
is configured for callback. If the username (hostname in the dialer
map
command) is not configured for callback, the initial call
stays up and no return call is made.
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