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Table Of Contents
Disable a Channel or Interface
NFAS Primary and Backup D Channels Example
PRI Interface Service State Example
NFAS with D Channel Back Up
Feature Summary
The DMS100 and NI2 switch types have been added to the existing Non-Facility Associated Signaling (NFAS) with D Channel Backup feature.
ISDN NFAS allows a single D channel to control multiple PRI interfaces. A backup D channel can be configured for use when the primary NFAS D channel fails.
Once the channelized T1controllers are configured for ISDN PRI, only the NFAS primary D channel must be configured; its configuration is distributed to all the members of the associated NFAS group.
Benefits
Use of a single D channel to control multiple PRI interfaces can free one B channel on each interface to carry other traffic.
Any hard failure causes a switchover to the backup D channel and currently connected calls remain connected.
Note
On the Nortel dms100 switch, when a single D channel is shared, multiple PRI interfaces may be configured in a single trunk group. The additional use of alternate route indexing, which is a feature of the dms100 switch, provides a rotary from one trunk group to another. This enables the capability of building large trunk groups in a public switched network.
List of Terms
24 B channel interface—A PRI channel group configured to have no NFAS D channel; all its channels are B channels.
NFAS group—A PRI channel group (the group of interfaces) under control of a single D channel. The channel group can include all the ISDN channels on multiple T1 controllers. Cisco IOS supports ten PRI interfaces in an NFAS group with a primary D channel and a backup D channel. Five NFAS groups are supported in a single chassis.
NFAS member—A PRI interface in an NFAS group. For example, an NFAS group might include serial interfaces 1/0:23, 1/1:23, and 2/0:23 if T1 controllers 1/0, 1/1, and 2/0 are configured for NFAS.
non-facility associated signaling (NFAS)—An ISDN service that allows a single D channel to control multiple PRI interfaces. Use of a single D channel to control multiple PRI interfaces can free one B channel on each interface to carry other traffic.
Restrictions
The following restrictions apply to this feature:
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Platforms
This feature is supported on these platforms:
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Prerequisites
The router's channelized T1 controllers must be configured for ISDN, as described in the "Configuring ISDN PRI" section of the "Configuring Channelized E1 and Channelized T1" chapter in the Cisco IOS Release 11.3 Dial Solutions Configuration Guide.
Supported MIBs and RFCs
None
Configuration Tasks
To configure NFAS with D channel back up, complete the following task:
You can also disable a channel or interface, if necessary, and monitor NFAS groups and ISDN service. To do so, complete the tasks in the following sections:
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Configure NFAS on PRI Groups
This section documents tasks used to configure NFAS with D channel backup. When configuring NFAS, you use an extended version of the ISDN pri-group command to specify the following values for the associated channelized T1 controllers configured for ISDN:
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To configure ISDN NFAS, complete the following tasks in controller configuration mode:
For an example of configuring three T1 controllers for the NFAS primary D channel, the backup D channel, and 24 B channels, along with the DDR configuration for the PRI interface, see the "NFAS Primary and Backup D Channels Example" section.
When a backup NFAS D channel is configured and the primary NFAS D channel fails, rollover to the backup D channel is automatic and all connected calls stay connected.
If the primary NFAS D channel recovers, the backup NFAS D channel remains active and does not switch over again unless the backup NFAS D channel fails.
Disable a Channel or Interface
You can disable a specified channel or an entire PRI interface, thus taking it out of service or put it into one of the other states that is passed in to the switch. To disable a specific channel or PRI interface, complete one of the following tasks in interface configuration mode:
These are the supported state values:
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Monitor NFAS Groups
To monitor NFAS groups, complete the following task in EXEC mode:
Monitor ISDN Service
To display information about ISDN channel service states, complete the following task in EXEC mode:
Configuration Examples
This section provides the following configuration examples:
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NFAS Primary and Backup D Channels Example
The following example configures ISDN PRI and NFAS on three T1 controllers of a Cisco 7500 series router. The NFAS primary D channel is configured on the 1/0 controller, and the NFAS backup D channel is configured on the 1/1 controller. No NFAS D channel is configured on the 2/0 controller; it is configured for 24 B channels.
Once the NFAS primary D channel is configured, it is the only interface you see and have to configure; DDR configuration for the primary D channel—which is distributed to all B channels—is also included in this example.
isdn switch-type primary-dms100!! NFAS primary D channel on the channelized T1 controller in 1/0controller t1 1/0framing esflinecode b8zspri-group timeslots 1-24 nfas_d primary nfas_interface 0 nfas_group 1!! NFAS backup D channel on the channelized T1 controller in 1/1controller t1 1/1framing esflinecode b8zspri-group timeslots 1-24 nfas_d backup nfas_interface 1 nfas_group 1!! NFAS 24 B channels on the channelized T1 controller in 2/0controller t1 2/0framing esflinecode b8zspri-group timeslots 1-24 nfas_d none nfas_interface 2 nfas_group 1!! NFAS primary D channel interface configuration for PPP and DDR. This! configuration is distributed to all the B channels in NFAS group 1 on the! three channelized T1 controllers.!interface Serial 1/0:23ip address 1.1.1.2 255.255.255.0no ip mroute-cacheencapsulation pppdialer map ip 1.1.1.1 name flyboy 567898dialer map ip 1.1.1.3 name flyboy 101112345678dialer map ip 1.1.1.4 name flyboy 01112345678dialer-group 1no fair-queueno cdp enableppp authentication chapPRI Interface Service State Example
The following example reenables the entire PRI interface after it previously had been disabled:
isdn service dsl 0 b-channel 0 state 0Command Reference
There are no new or modified commands for this feature. Existing commands used to configure this feature are documented in the Cisco IOS Release 11.3 command references.
