5.5 ISDN Configuration Tasks
5.5.4 Write the IOS commands pertaining to SPIDs

SPIDs allow multiple ISDN devices, such as voice and data devices, to share the local loop. In many cases, such as when you're configuring the router to connect to a DMS-100, you need to input the SPIDs.

Remember that ISDN is typically used for dialup connectivity. The SPIDs are processed during each call setup operation. You use the isdn spid2 command in interface configuration mode to define at the router the SPID number that has been assigned by the ISDN service provider for the B2 channel. The full syntax of the command is isdn spid2 spid-number [ldn]. The optional LDN command is for a local dial directory number.  On most switches, the number must match the called party information coming in from the ISDN switch in order to use both B channels.

You use the no isdn spid2 command to disable the specified SPID, thereby preventing access to the switch. If you include the LDN (Local Directory Number) in the no form of this command, the access to the switch is permitted, but the other B channel might not be able to receive incoming calls. The full syntax of the command is:

no isdn spid2 spid-number [ldn]

The spid-number  argument indicates the number identifying the service to which you have subscribed. This value is assigned by the ISDN service provider and is usually a 10-digit telephone number with some extra digits. By default, no SPID number is defined.

Engineering Journal
  DMS-100 Switches
Engineering Journal
  The ldn Argument