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Digital modems and ISDN Pri

I am trying to configure integrated digital modem via ISDN-PRI link on a cisco 3660 router. Following is the basic configuration;

( using NM-30DM and NM-1CE1B modules);

hostname Router



modem country mica united-kingdom

ip subnet-zero


isdn switch-type primary-net5

modemcap entry mica


controller E1 4/0

pri-group timeslots 1-31



interface Loopback0

ip address



interface Serial4/0:15

ip unnumbered Loopback0

encapsulation ppp

isdn switch-type primary-qsig

isdn incoming-voice modem

isdn T310 40000

isdn negotiate-bchan

isdn bchan-number-order ascending


interface Group-Async1

ip unnumbered Loopback0

encapsulation ppp

dialer in-band

dialer pool-member 2

async mode dedicated

no peer default ip address

ppp authentication chap

group-range 161 190


line con 0

line 161 190

modem InOut

modem autoconfigure type mica

transport input all

line aux 0

line vty 0 4



ISDN seems to be OK as per the following 'sh isdn status';

Router#sh isdn status

Global ISDN Switchtype = primary-net5

ISDN Serial4/0:15 interface

dsl 0, interface ISDN Switchtype = primary-qsig

**** Slave side configuration ****

Layer 1 Status:


Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = TEI_ASSIGNED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 0 CCBs = 0

The Free Channel Mask: 0x7FFF7FFF

Number of L2 Discards = 0, L2 Session ID = 1

Total Allocated ISDN CCBs = 0

But, when I try to make a dial using internal digital modems, I get the following error message;

01:39:26: ISDN Serial4/0:15: isdn_is_bchannel_available: No Free B-channels

I try to change the b-channel selection order ( ascending /descending) and other parameters, but still no improvement.

What could be the possible reasion ?


Re: Digital modems and ISDN Pri

I beleive that on interface Serial4/0:15 you are missing dialer-pool 2 statement , this maps the physiacl int to the virtual interface

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