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Configuring Dial-In and Callback (Optional)

If you are a service provider or a corporate data center into which a remote location dials in during an emergency, you can configure the Services Router to accept incoming ISDN calls originating from the remote location, or reject the incoming calls and call back the remote location. The callback feature lets you control access by allowing only specific remote locations to connect to the Services Router. You can also configure the Services Router to reject all incoming ISDN calls.

Note: Incoming voice calls are currently not supported.

When it receives an incoming ISDN call, the Services Router matches the incoming call's caller ID against the caller IDs configured on its dialer interfaces. If an exact match is not found and the incoming call's caller ID has more digits than the configured caller IDs, the Services Router performs a right-to-left match of the incoming call's caller ID with the configured caller IDs and accepts the incoming call if a match is found. For example, if the incoming call's caller ID is 4085550115 and the caller ID configured on a dialer interface is 5550115, the incoming call is accepted. Each dialer interface accepts calls from only callers whose caller IDs are configured on it.

The dialer interface of the Services Router and the dialer interface of the remote router must have the same encapsulation—PPP, Multilink PPP, or Cisco HDLC. If the encapsulation is different, the ISDN call is dropped. Table 68 describes how the Services Router performs encapsulation monitoring.

Table 68: Encapsulation Monitoring by Services Routers

Encapsulation on Services Router's Dialer Interface	Encapsulation on Remote Router's Dialer Interface	Possible Action on Services Router's Dialer Interface	Encapsulation Monitoring and Call Status
PPP	PPP	Accepts an incoming call Rejects an incoming call and calls back the incoming number when callback is enabled on the dialer interface	Services Router performs encapsulation monitoring. ISDN call is successful because encapsulation matches.
Multilink PPP	Multilink PPP
PPP	Multilink PPP or Cisco HDLC		Services Router performs encapsulation monitoring. ISDN call is dropped because of encapsulation mismatch.
Multilink PPP	PPP or Cisco HDLC
PPP or Multilink PPP	PPP, Multilink PPP, or Cisco HDLC	Dials out Accepts an incoming call as a result of having originally dialed out, because the dialer interface of the remote router has callback enabled	Services Router does not perform encapsulation monitoring. Success of the ISDN call depends on the encapsulation monitoring capability of the remote router.
Cisco HDLC	PPP, Multilink PPP, or Cisco HDLC	Dials out Accepts an incoming call Accepts an incoming call as a result of having originally dialed out, because the dialer interface of the remote router has callback enabled Rejects an incoming call and calls back the incoming number when callback is enabled on the dialer interface

This section contains the following topics:

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