Many time during our engineering graduation and at the time of networking career came across E1/T1 link.
I was thinking of writing or discussing this in the blog keeping very basic fundamental of these and a few initial configuration that we do to make it work.
E1 and T1 are the carrier and ISDN PRI work over it. The ISDN are of two type BRI and PRI The PRI has two options.
T1 - In this the ISDN contain 23 B channel and 1 D channel (Control channel for ISDN)
E1- In this the ISDN contain 30 B + 1 D channel
I am going to discuss NFAS in this post ..
NFAS: Nfas is a function of Pri where 1 D channel control multiple pri , To a Max 1 D channel in NFAS can control 478 B Channel , In NFAS for sake of redundancy you can also define a secondary D channel apart from the primary one
Configuration command for NFAS:
pri-group timeslots 1-24 nfas_d function nfas_interface int_number nfas_group group_number
function - The function to be performed by timeslot 24, either primary, backup, or none. Every NFAS group must have one primary. The router does not require a backup, however most NFAS implementations
do have a backup D channel. Contact your telco to determine whether you should configure a backup D channel for your NFAS group. The rest of the controllers can be configured with none, which designates the 24th timeslot as a B channel.
int_number - A value assigned by the service provider and used to uniquely identify the PRI. The values possible range from 0 to the highest t1 available on the router, minus one. For example, if the router has 10 T1s the NFAS interface number can range betweeen 0 and 9. The 0 interface must be assigned to the primary D channel and the 1 interface to the backup D channel.
group_number - Group identifier unique on the router. Multiple NFAS groups can exist on the router. Each group must be configured with a primary and secondary controller.
Never user Interface id number as 1 if you are planning to implement backup D Channel
Sample Config:
isdn switch-type primary-ni
controller T1 0
framing esf
clock source line primary
linecode b8zs
pri-group timeslots 1-24 nfas_d primary nfas_int 0 nfas_group 0
!
controller T1 1
framing esf
clock source line secondary 1
linecode b8zs
pri-group timeslots 1-24 nfas_d backup nfas_int 1 nfas_group 0
!
controller T1 2
framing esf
clock source line secondary 2
linecode b8zs
pri-group timeslots 1-24 nfas_d none nfas_int 2 nfas_group
Here Controller T1 has the primary D channel and all has been binded to group 0 with command parameter "nfas_group 0"..
Command that is helpful in troubleshooting idsn issue is
Debug isdn q931..
I was thinking of writing or discussing this in the blog keeping very basic fundamental of these and a few initial configuration that we do to make it work.
E1 and T1 are the carrier and ISDN PRI work over it. The ISDN are of two type BRI and PRI The PRI has two options.
T1 - In this the ISDN contain 23 B channel and 1 D channel (Control channel for ISDN)
E1- In this the ISDN contain 30 B + 1 D channel
I am going to discuss NFAS in this post ..
NFAS: Nfas is a function of Pri where 1 D channel control multiple pri , To a Max 1 D channel in NFAS can control 478 B Channel , In NFAS for sake of redundancy you can also define a secondary D channel apart from the primary one
Configuration command for NFAS:
pri-group timeslots 1-24 nfas_d function nfas_interface int_number nfas_group group_number
function - The function to be performed by timeslot 24, either primary, backup, or none. Every NFAS group must have one primary. The router does not require a backup, however most NFAS implementations
do have a backup D channel. Contact your telco to determine whether you should configure a backup D channel for your NFAS group. The rest of the controllers can be configured with none, which designates the 24th timeslot as a B channel.
int_number - A value assigned by the service provider and used to uniquely identify the PRI. The values possible range from 0 to the highest t1 available on the router, minus one. For example, if the router has 10 T1s the NFAS interface number can range betweeen 0 and 9. The 0 interface must be assigned to the primary D channel and the 1 interface to the backup D channel.
group_number - Group identifier unique on the router. Multiple NFAS groups can exist on the router. Each group must be configured with a primary and secondary controller.
Never user Interface id number as 1 if you are planning to implement backup D Channel
Sample Config:
isdn switch-type primary-ni
controller T1 0
framing esf
clock source line primary
linecode b8zs
pri-group timeslots 1-24 nfas_d primary nfas_int 0 nfas_group 0
!
controller T1 1
framing esf
clock source line secondary 1
linecode b8zs
pri-group timeslots 1-24 nfas_d backup nfas_int 1 nfas_group 0
!
controller T1 2
framing esf
clock source line secondary 2
linecode b8zs
pri-group timeslots 1-24 nfas_d none nfas_int 2 nfas_group
Here Controller T1 has the primary D channel and all has been binded to group 0 with command parameter "nfas_group 0"..
Command that is helpful in troubleshooting idsn issue is
Debug isdn q931..
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