ISDN Voice Configuration Guide, Cisco IOS Release 15M&T
NFAS with D-Channel Backup
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NFAS with D-Channel Backup

NFAS with D-Channel Backup

Last Updated: December 4, 2012

This chapter describes how to implement the Non-Facility Associated Signaling (NFAS) with D-Channel Backup feature with two new switch types: DMS100 and NI2. ISDN NFAS allows a single D channel to control multiple ISDN PRI interfaces. You can configure a backup D channel for use when the primary NFAS D channel fails.

After you configure channelized T1 controllers for ISDN PRI, you only need to configure the NFAS primary D channel; its configuration is distributed to all the members of the associated NFAS group.


Note


A controller configured with backup D channel loses one B channel.

Use of a single D channel to control up to 10 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. The backup D channel cannot be used for data transfer.


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.

Feature History for NFAS with D-Channel Backup

Release

Modification

12.1(5)XM

This feature was introduced.

12.2(11)T

This feature was implemented on the Cisco AS5850 platform.

12.4(24)T

NFAS network-side support was added.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for Configuring NFAS with D-Channel Backup

  • Perform the prerequisites that are listed in the "Prerequisites for Configuring an ISDN Voice Interface" section.
  • Configure your router's channelized T1 controllers for ISDN, as described in the "Configuring ISDN PRI" section of the "Configuring Channelized E1 and Channelized T1" chapter in the Dial Solutions Quick Configuration Guide.

Restrictions for Configuring NFAS with D-Channel Backup

Restrictions are described in "Restrictions for Configuring ISDN Voice Interfaces". In addition, the following apply:

  • NFAS is supported with only a channelized T1 controller and, as a result, is ISDN PRI capable.
  • NFAS is supported across multiple T1 controllers installed on different slots only if the DSPs of those slots are of the same type. For example, if T1 controllers on slot 1 and slot 2 are combined to form an NFAS group with the T1 in slot 1 being primary, both slots must have the same type of DSP. If these two slots have different DSP types, only those calls using T1 on slot 1 will connect --all calls through T1 on slot 2 will fail with a disconnect cause of "Resource Unavailable/Unspecified (47)."
  • The router must connect to either a 4ess, dms250, dms100, or National ISDN switch type. The table below shows applicable ISDN switch types and supported NFAS types.
Table 1 ISDN Switch Types and Supported NFAS Types

ISDN Switch Type

NFAS Type

Lucent 4ESS

Custom NFAS

Nortel DMS250

Custom NFAS

Nortel DMS100

Custom NFAS

Lucent 5ESS

Custom; does not support NFAS

Lucent 5ESS

NI-2 NFAS

AGCS GTD5

NI-2 NFAS

Other switch types

NI-2 NFAS

Network-side

Network-side emulation

Information about NFAS

Non-Facility Associated Signaling is a classification of signalling protocols that provide the signalling channel in a separate physical line from the bearer channels.


Note


General information about ISDN voice interfaces is presented in the "Information About ISDN Voice Interfaces" section.

How to Configure NFAS with D-Channel Backup

Configuring NFAS on PRI Groups

To configure NFAS on PRI groups, perform the following steps.


Note


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.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    controller {t1 | e1} controller-number

4.    pri-group timeslots range nfas_d primary nfas_interface number nfas_group number

5.    pri-group timeslots range nfas_d backup nfas_interface number nfas_group number

6.    pri-group timeslots range nfas_d none nfas_int number nfas_group number

7.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enters privileged EXEC mode. Enter your password when prompted.

 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters configuration mode.

 
Step 3
controller {t1 | e1} controller-number


Example:

Router(config)# controller t1 3

 

Enters controller configuration mode for the specified controller number.

 
Step 4
pri-group timeslots range nfas_d primary nfas_interface number nfas_group number


Example:

Router(config-controller)# pri-group timeslots 1-24 nfas_d primary nfas_interface 1 nfas_group 1

 

Configures, on one channelized T1 controller, the NFAS primary D channel. Keywords are as follows:

  • nfas_interface number --Value assigned by the service provider to ensure unique identification of a PRI interface.
  • nfas_group number --Group identifier unique on the router. Multiple NFAS groups can exist on the router.

The interface number is the number of the interface assigned to an interface that is part of an nfas group. All interfaces that are part of an nfas group have the same group number and each is identified uniquely within the group by the interface number.

 
Step 5
pri-group timeslots range nfas_d backup nfas_interface number nfas_group number


Example:

Router(config-controller)# pri-group timeslots 1-24 nfas_d backup nfas_interface 2 nfas_group 1

 

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

Repeat this step on other channelized T1 controllers, as appropriate.

 
Step 6
pri-group timeslots range nfas_d none nfas_int number nfas_group number


Example:

Router(config-controller)# pri-group timeslots 1-24 nfas_d none nfas_int 3 nfas_group 1

 

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

 
Step 7
exit


Example:

Router(config-controller)# exit

 

Exits the current mode.

 

Configuring a VoIP Dial Peer for NFAS Voice

To configure a VoIP dial peer for NFAS voice, perform the following steps.


Note


Dial peers are used by the Cisco IOS voice stack for handling calls going from the PSTN to the VoIP side or vice versa. The dial-peer configuration for each NFAS controller should contain the primary of the NFAS group.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    dial-peer voice tag voip

4.    port controller :D

5.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enters privileged EXEC mode. Enter your password when prompted.

 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters configuration mode.

 
Step 3
dial-peer voice tag voip


Example:

Router(config)# dial-peer voice 99 voip

 

Enters dial-peer configuration mode for the specified VoIP dial peer.

 
Step 4
port controller :D


Example:

Router(config-dial-peer)# port 4:D

 

Associates the dial peer with a specific voice port--in this case, the D channel associated with ISDN PRI for the NFAS primary.

 
Step 5
exit


Example:

Router(config-dial-peer)# exit

 

Exits the current mode.

 

Disabling a Channel or Interface

To disable a channel or interface, perform the following steps.


Note


You can disable a specified channel or an entire PRI, thus taking it out of service or put it into one of the other states that is passed in to the switch.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface serial controller-number : timeslot

4.    isdn service [dsl number | nfas_int number] b_channel number state{0 | 1 | 2}

5.    isdn service [dsl number | nfas_int number] b_channel number state {0 | 1 | 2}

6.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enters privileged EXEC mode. Enter your password when prompted.

 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters configuration mode.

 
Step 3
interface serial controller-number : timeslot


Example:

Router(config)# interface serial 4/1:23

 

Enters interface configuration mode and specifies a serial interface for ISDN PRI, channel-associated signaling, or robbed-bit signaling.

 
Step 4
isdn service [dsl number | nfas_int number] b_channel number state{0 | 1 | 2}


Example:

Router(config-if)# isdn service nfas_int 3 b_channel 1 state 1

 

Takes an individual B channel out of service or sets it to a different state. State values are as follows:

  • 0 --In service
  • 1 --Maintenance
  • 2 --Out of service
 
Step 5
isdn service [dsl number | nfas_int number] b_channel number state {0 | 1 | 2}


Example:

Router(config-if)# isdn service nfas_int 3 b_channel 0 state 1

 

As above. Setting the b-channel number to 0 sets the entire PRI interface to a specified state value.

 
Step 6
exit


Example:

Router(config-if)# exit

 

Exits the current mode.

 

Verifying NFAS Configuration

To verify NFAS configuration, perform the following steps (listed alphabetically).

SUMMARY STEPS

1.    show dial-peer voice

2.    show isdn nfas group

3.    show isdn service

4.    show isdn status

5.    show running-config


DETAILED STEPS
Step 1   show dial-peer voice

Use this command to display the configuration information for dial peers.



Example:
Router# show dial-peer voice
VoiceOverIpPeer1
        information type = voice,
        tag = 1, destination-pattern = `',
        answer-address = `', preference=0,
        numbering Type = `unknown'
        group = 1, Admin state is up, Operation state is down,
        incoming called-number = `', connections/maximum = 0/unlimited,
        DTMF Relay = disabled,
        modem passthrough = system,
        huntstop = disabled,
        in bound application associated: DEFAULT
        out bound application associated:
        permission :both
        incoming COR list:maximum capability
        outgoing COR list:minimum requirement
        type = voip, session-target = `',
        technology prefix:
        settle-call = disabled
        ip precedence = 0, UDP checksum = disabled,
        session-protocol = cisco, session-transport = udp, req-qos = best-effor
        acc-qos = best-effort,
        fax rate = voice,   payload size =  20 bytes
        fax protocol = system
        fax NSF = 0xAD0051 (default)
        codec = g729r8,   payload size =  20 bytes,
        Expect factor = 0, Icpif = 20,
        Playout: Mode adaptive,
        Expect factor = 0,
        Max Redirects = 1, Icpif = 20,signaling-type = cas,
        CLID Restrict = disabled
        VAD = enabled, Poor QOV Trap = disabled,
        voice class perm tag = `'
        Connect Time = 0, Charged Units = 0,
        Successful Calls = 0, Failed Calls = 0,
        Accepted Calls = 0, Refused Calls = 0,
        Last Disconnect Cause is "",
        Last Disconnect Text is "",
        Last Setup Time = 0.
Step 2   show isdn nfas group

Use this command to display information about members of an NFAS group.



Example:
Router# show isdn nfas group 1
ISDN NFAS GROUP 1 ENTRIES:
The primary D is Serial1/0:23.
The backup D is Serial1/1:23.
The NFAS member is Serial2/0:23.
There are 3 total nfas members.
There are 93 total available B channels.
The primary D-channel is DSL 0 in state INITIALIZED.
The backup D-channel is DSL 1 in state INITIALIZED.
The current active layer 2 DSL is 1.
Step 3   show isdn service

Use this command to display information about ISDN channels and the service states.

Step 4   show isdn status

Use this command to display the status of all ISDN interfaces, including active layers, timer information, and switch-type settings.

Step 5   show running-config

Use this command to display the basic router configuration.


Examples

This section provides the following output examples:

Sample Output for the show isdn nfas group Command

The following three examples show D channel state changes when rollover occurs from the primary NFAS D channel to the backup D channel. The first example shows the output with the primary D channel in service and the backup D channel in standby.

Router# show isdn nfas group 0
ISDN NFAS GROUP 0 ENTRIES:
The primary D is Serial1/0:23.
The backup D is Serial1/1:23.
The NFAS member is Serial2/0:23.
There are 3 total nfas members.
There are 70 total available B channels.
The primary D-channel is DSL 0 in state IN SERVICE.
The backup D-channel is DSL 1 in state STANDBY.
The current active layer 2 DSL is 0.

The following example shows output during rollover. The configured primary D channel is in maintenance busy state and the backup D channel is waiting.

Router# show isdn nfas group 0
ISDN NFAS GROUP 0 ENTRIES:
The primary D is Serial1/0:23.
The backup D is Serial1/1:23.
The NFAS member is Serial2/0:23.
There are 3 total nfas members.
There are 70 total available B channels.
The primary D-channel is DSL 0 in state MAINTENANCE BUSY.
The backup D-channel is DSL 1 in state WAIT.
The current active layer 2 DSL is 1.

The following example shows output when rollover is complete. The configured primary D channel is now in standby and the backup D channel is in service.

Router# show isdn nfas group 0
ISDN NFAS GROUP 0 ENTRIES:
The primary D is Serial1/0:23.
The backup D is Serial1/1:23.
The NFAS member is Serial2/0:23.
There are 3 total nfas members.
There are 70 total available B channels.
The primary D-channel is DSL 0 in state STANDBY.
The backup D-channel is DSL 1 in state IN SERVICE.
The current active layer 2 DSL is 1.

Configuration Examples for NFAS with D-Channel Backup

NFAS Primary and Backup D Channels Example

The following example configures ISDN PRI and NFAS on multiple T1 controllers of a Cisco 7500 series router. The D-channel of T1 1/0/0 is configured as primary D-channel and T1 1/0/1 is configured as backup D-channel. Once you configure the NFAS primary D channel, that channel is the only interface you see and have to configure.

version 12.x
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
!
hostname travis-nas-01
!
aaa new-model
aaa authentication login default local
aaa authentication login NO_AUTHENT none
aaa authorization exec default local if-authenticated
aaa authorization exec NO_AUTHOR none
aaa authorization commands 15 default local if-authenticated
aaa authorization commands 15 NO_AUTHOR none
aaa accounting exec default start-stop group tacacs+
aaa accounting exec NO_ACCOUNT none
aaa accounting commands 15 default stop-only group tacacs+
aaa accounting commands 15 NO_ACCOUNT none
enable secret 5 $1$LsoW$K/qBH9Ih2WstUxvazDgmY/
!
username admin privilege 15 password 7 06455E365E471D1C17
username gmcmilla password 7 071824404D06140044
username krist privilege 15 password 7 0832454D01181118
!
call rsvp-sync
shelf-id 0 router-shelf
shelf-id 1 dial-shelf
!
resource-pool disable
!
modem-pool Default
 pool-range 1/2/0-1/2/143,1/3/0-1/3/143
!
clock timezone CST -6
clock summer-time CST recurring
!
ip subnet-zero
ip domain-name cisco.com
ip name-server 172.22.53.210
ip name-server 171.69.2.133
ip name-server 171.69.2.132
ip name-server 171.69.11.48
!
isdn switch-type primary-5ess
isdn voice-call-failure 0
!
controller T1 1/0/0
 framing esf
 linecode b8zs
 pri-group timeslots 1-24 nfas_d primary nfas_interface 1 nfas_group 1
 description PacBell 3241933
!
controller T1 1/0/1
 framing esf
 linecode b8zs
 pri-group timeslots 1-24 nfas_d backup nfas_interface 2 nfas_group 1
 description PacBell 3241933
!
interface Loopback0
 ip address 172.21.10.1 255.255.255.255
!
interface FastEthernet0/0/0
 ip address 172.21.101.20 255.255.255.0
 half-duplex
!
interface Serial1/0/0:23
 no ip address
 ip mroute-cache
 isdn switch-type primary-5ess
 isdn incoming-voice modem
 no cdp enable
!
interface Group-Async0
 no ip address
 group-range 1/2/00 1/3/143
!
router eigrp 1
 network 172.21.0.0
 no eigrp log-neighbor-changes
!
ip classless
ip route 0.0.0.0 0.0.0.0 172.21.101.1

ip http server

ip http authentication aaa
!
snmp-server engineID local 0000000902000030F2F51400
snmp-server community 5urf5h0p RO
snmp-server community 5crapmeta1 RW
snmp-server community SNMPv1 view v1default RO

POTS Dial-Peer Configuration Example

The following example shows configuration of a POTS dial peer with the primary controller of an NFAS group:

dial-peer voice 35 pots
		incoming called-number 45...
destination-pattern 35...
direct-inward-dial
port 1/0/0:D
prefix 35

PRI Service State Example

The following example reenables the entire PRI after it was disabled:

isdn service dsl 0 b-channel 0 state 0

Additional References

General ISDN References

  • "Overview of ISDN Voice Interfaces" --Describes relevant underlying technology; lists related documents, standards, MIBs, and RFCs; and describes how to obtain technical assistance
  • "Additional References" section --Lists additional ISDN references

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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