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110 Chapter 5: Configuring PPP and Controlling Network Access
Example 5-4 shows the PPP Callback configuration for the server.
The callback client uses the ppp callback request command to request that the callback occur.
The server router uses the ppp callback accept command as an indication that it should accept
callback requests and place a call to the phone number configured for the requesting client (in
this case, 5553434).
The dialer callback-secure command disconnects calls that are not properly configured for
callback. It also forces a disconnect of any unconfigured dial-in users. 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.
Figure 5-6 illustrates the PPP Callback procedure.
Example 5-3
PPP Callback Client Configuration
Client(config)#username Client password cisco
Client(config)#username Server password cisco
Client(config)#dialer-list 1 protocol ip permit
Client(config)#interface S0
Client(config-if)#ip address 10.1.1.1 255.255.255.0
Client(config-if)#encapsulation ppp
Client(config-if)#dialer map ip 10.1.1.2 name Server 5551212
Client(config-if)#dialer-group 1
Client(config-if)#ppp callback request
Client(config-if)#ppp authentication chap
Client(config-if)#dialer hold-queue timeout 30
Example 5-4
PPP Callback Server Configuration
Server(config)#username Client password cisco
Server(config)#username Server password cisco
Server(config)#dialer-list 1 protocol ip permit
Server(config)#interface S0
Server(config-if)#ip address 10.1.1.1 255.255.255.0
Server(config-if)#encapsulation ppp
Server(config-if)#dialer callback-secure
Server(config-if)#dialer map ip 10.1.1.1 name Client 5553434
Server(config-if)#dialer-group 1
Server(config-if)#ppp callback accept
Server(config-if)#ppp authentication chap