Cisco Cisco IOS Software Release 12.2(8)YN

When configuring NFAS, use an extended version of the ISDN pri-group command to specify the 
following values for the associated channelized T1 controllers configured for ISDN:

The range of PRI time slots to be under the control of the D channel (timeslot 24).

The function to be performed by time slot 24 (primary D channel, backup, or none); the latter 
specifies its use as a B channel.

The group identifier number for the interface under this D channel’s control.

To configure ISDN NFAS, complete the following tasks in controller configuration mode:

For additional information about ISDN PRI configuration, refer to the “Configuring ISDN Interfaces for 
Voice” section in the “Configuring the Cisco ICS 7750” chapter of the 

. For detailed ISDN PRI configuration instructions, refer to the “Configuring ISDN 

PRI” chapter in “Part 4, Signaling Configuration” in the 

.

The following restrictions apply when using NFAS on MRPs in the Cisco ICS 7750: 

NFAS is not supported between two MRPs.

MGCP is not supported when using NFAS—you must use H.323 in order to use NFAS.

NFAS must be configured on your service provider’s ISDN switch.

Only the switch types shown in 

 support NFAS.

pri-group timeslots 1-24 nfas_d primary nfas_int number            
nfas_group number 

Configures, on one channelized T1 controller, the 
NFAS primary D channel.

pri-group timeslots 1-24 nfas_d backup nfas_int number            
nfas_group number 

Configures, on a different channelized T1 controller, 
the NFAS backup D channel to be used if the 
primary D channel fails. 

pri-group timeslots 1-24 nfas_d none nfas_int number            
nfas_group number

(Optional) Configures, on other channelized T1 
controllers, a 24 B channel interface.

AGCS GTD5  

NI-2 NFAS

Lucent 4ESS

Custom NFAS

Lucent 5ESS

NI-2 NFAS

Nortel DMS100

Custom NFAS

Nortel DMS250

Custom NFAS

Other switch types

NI-2 NFAS