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ISDN Configuration BasicsNow that the boring specifics of ISDN are behind us, it is time to dive into the more interesting topic of how to actually configure Cisco routers to use ISDN. Unfortunately, there is currently no method of configuring ISDN in a lab environment without the use of actual ISDN circuits or a costly ISDN simulator. Nonetheless, ISDN is a core topic in the CCIE routing and switching lab exam, and the only way to learn the topic is through a great deal of hands-on practice. To configure basic ISDN, only two things must be configured:
The SPID is a number assigned to a fully initializing ISDN terminal that enables the Stored Program Control Switching System (SPCS) to uniquely identify the ISDN terminal at Layer 3 of the D-channel signaling protocol. A SPID is assigned to each B channel and usually resembles a phone number followed by some extra digits. For example, if your router is connecting to a Siemens ISDN switch, the SPIDs would typically be of the type aaabbbbbbbccdd, where
For national ISDN switches, the most frequently used SPID value is NPANXXXXXX0101, based on the configurations being installed today. The NPA/NXX is simply the carrier's term for the local area code/access number. Not all ISDN switches actually require that the SPIDS be configured, but the majority of them do. The ISDN provider can provide you with the information that you need. Currently, Cisco routers support a number of different switch type options, as documented in Table 7-1. Table 7-1. Supported ISDN Switch Types
You need to contact your ISDN service provider to determine which switch type is being used. The switch type can be configured in both global and interface configuration modes. If it is specified in global mode, the switch type applies to all ISDN interfaces in the router. If it is placed in interface mode, it is applied to the interface only. If both are specified, the switch type that is configured in interface mode overrides the switch type set globally for that interface. For example, if you have a router with six ISDN interfaces and five of them connect to a DMS-100 switch, with the other connecting to an NI switch, you can use the isdn switch-type basic-dms100 command globally and then use the command isdn switch-type basic-ni in interface mode for the specific NI connected BRI interface. |
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