When you configure the T1 controller, two corresponding D-channel serial interfaces are instantly created. You must configure each serial interface to receive incoming and send outgoing modem signaling. Note The ISDN switch type should match the telco switch type. Configure the switch type using the isdn switch-type global configuration command. In North America, the options are NI1, 5ESS, and DMS 100.
Options are more varied in other countries.
The framing and line code you configure must match your telco's offering, which in most cases is esf and b8zs . Step 3 Configure one T1 line to serve as the primary or most stable clock source line. Step 4 Specify how you want to configure all 24 channels. You must configure this command on both T1 controllers if you want to support the CSU functionality. However, you must use the same facilities data link exchange standard as your service provider.