We have a custom application that connects through reverse telnet to a Cisco 3640 that has 2 NM-24DM modules and 2 PRIs connected to it. Currently all outgoing calls are getting load balanced over the two PRIs. I need to change that so that all calls go over the first PRI and when all channels are used up, it starts using the second PRI. Seems like a simple enough thing to do but I can't figure out how to.

Here is my config

Current configuration : 1401 bytes
!
version 12.4
service timestamps debug uptime
service timestamps log uptime
service password-encryption
!
hostname DIALOUT01
!
boot-start-marker
boot-end-marker
!
enable secret 5 xxxxxxx
!
no aaa new-model
clock timezone EST -5
clock summer-time EDT recurring
no ip routing
!
!
no ip cef
no ip domain lookup
ip domain name xxxxxxx.xxx
!
!
isdn switch-type primary-ni
!
!
!
controller T1 0/0
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
!
controller T1 0/1
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
!
!
!
interface FastEthernet0/0
ip address dhcp hostname dialout01
no ip route-cache
no ip mroute-cache
duplex auto
speed auto
!
interface Serial0/0:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
!
interface Serial0/1:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
!
no ip http server
!
!
!
!
control-plane
!
!
line con 0
line 33 56
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line 65 88
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line aux 0
line vty 0 4
password 7 xxxxx login
!
!
end

Thanks,

Shahid