Combining ISDN services/cards on a Cisco IOS router is simple to do and saves a lot time trying to configure dial-peer preferences for outbound calling.

BRI Interfaces can be added to a ‘Tunnel-Group’, the tunnel-group can now be the base for translations rules, dial-peer legs and other voice configuration on a Cisco ISR.

By directing the dial-peer to the Tunnel-Group instead of individual voice ports, we can have a faster failover then using by using preferences and relying of configured timers.

Below is a snippet of some Cisco IOS configuration to combine 4x BRI Interfaces (8 voice channels) and tie them to a dial-peer for outbound call legs.

trunk group BRI-GROUP
hunt-scheme sequential both down

interface BRI0/0/0
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn sending-complete
isdn outgoing display-ie
isdn outgoing ie redirecting-number
isdn static-tei 0
trunk-group BRI-GROUP

interface BRI0/0/1
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn sending-complete
isdn outgoing display-ie
isdn outgoing ie redirecting-number
isdn static-tei 0
trunk-group BRI-GROUP

interface BRI0/1/0
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn sending-complete
isdn outgoing display-ie
isdn outgoing ie redirecting-number
isdn static-tei 0
trunk-group BRI-GROUP

interface BRI0/1/1
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn sending-complete
isdn outgoing display-ie
isdn outgoing ie redirecting-number
isdn static-tei 0
trunk-group BRI-GROUP

Dial-peer voice 1 pots
trunkgroup BRI-GROUP
description ## Emergency Calls ##
destination-pattern 000
forward-digits all