CAS is a form of signaling used on a T1 line. With CAS, a signaling element is dedicated to each channel in the T1 frame. This type of signaling is sometimes called Robbed Bit Signaling (RBS) because a bit is taken out (or robbed) from the user's data stream to provide signaling information to and from the switch. The T1 CAS feature enables the modems on the Digital Network Modem Module to receive and transmit incoming and outgoing call signaling (such as on-hook and off-hook) through each T1 controller that is configured for a channelized T1 line.

• Install a T1 network module and another module (such as Ethernet) to provide connectivity to the LAN. Digital modem network modules do not provide physical network interfaces of their own, but instead handle analog calls passing through the T1 network module. If the T1 module has two ports, it is capable of concurrently handling digital ISDN data and remote voice-channel (analog) modem connections. The digital modem module provides a pool of available modems that can be used for both incoming and outgoing calls.

For information on how to install a T1 network module, refer to the 1-Port and 2-Port ISDN-PRI Network Module Configuration Note. For information on how to install an Ethernet module, refer to the 1-Port Ethernet Network Module Configuration Note or the 4-Port Ethernet Network Module Configuration Note. For other modules, refer to the specific configuration notes pertaining to them.

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Note The T1 module must be hardware revision -03; earlier revisions are incompatible with digital modem modules. For more information, refer to the "Software and Hardware Requirements" section in the Digital Modem Network Module Configuration Notes.

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• Install the Digital Modem Network Module in a chassis slot. For information on how to correctly install this network module, refer to the "Installing a Digital Modem Network Module in a Chassis Slot" section in the Digital Modem Network Module Configuration Note.

• Complete basic device configuration, including host name, username, protocol, and security configuration. For more information about basic device configuration, refer to the Cisco 3640 Installation and Configuration Guide.

• Make sure that you have the following T1 CAS information:

  • Line code

  • Framing type

  • Signaling type

This feature supports the following Management Information Bases (MIBs):

• CISCO-MODEM-MGMT-MIB

• CISCO-POP-MGMT-MIB

For descriptions of supported MIBs and how to use MIBs, see Cisco's MIB website on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.

For more information about configuring ISDN PRI on a channelized T1 controller, refer to the "Configure ISDN PRI" section of the Cisco IOS Release 11.3 Dial Solutions Configuration Guide.

To configure the loopback 0 interface, perform the following tasks, beginning in global configuration mode:

To configure an Ethernet interface, perform the following tasks, beginning in global configuration mode:

To configure a group asynchronous interface, perform the following tasks, beginning in global configuration mode:

For more information about group asynchronous interfaces, refer to the "Asynchronous Configuration Task List" section of the Cisco IOS Release 11.3 Dial Solutions Configuration Guide.

For more information about defining IP pool information, refer to the Cisco IOS Release 11.3 Network Protocols Configuration Guide, Part 1.

This configuration procedure ensures that a user trying to dial out using Telnet is connected to the first free line in the rotary group.

The Cisco 3640 has the following hardware configuration for this scenario:

• One 2-port T1 network module installed in slot 1

• One digital modem network module installed in slot 2 and slot 3

• One 1-port Ethernet network module installed in slot 0

Following is the configuration for the Cisco 3640.

!
version 11.2
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
no service udp-small-servers
no service tcp-small-servers
!
hostname NAS
!
aaa new-model
aaa authentication login default local
aaa authentication login console enable
aaa authentication login vty local
aaa authentication login dialin local
aaa authentication ppp default local
aaa authentication ppp dialin if-needed local
enable secret cisco
!
username admin password cisco
username remotelan1 password dialpass1
username remotelan2 password dialpass2
username PCuser1 password dialpass3
username PCuser2 password dialpass4
async-bootp dns-server 10.1.3.1 10.1.3.2
isdn switch-type primary-5ess
!
controller T1 1/0
 framing esf
 clock source line 
 linecode b8zs
 cas-group 0 timeslots 1-24 type fxs-loopstart
!
controller T1 1/1
 framing esf
 clock source line 
 linecode b8zs
 cas-group 0 timeslots 1-24 type fxs-loopstart
!
interface Loopback0
 ip address 10.1.2.254 255.255.255.0
!
interface Ethernet0/0
 ip address 10.1.1.10 255.255.255.0
 ip summary address eigrp 10 10.1.2.0 255.255.255.0
!
interface Group-Async1
 ip unnumbered Loopback0
 encapsulation ppp
 async mode interactive
 peer default ip address pool dialin_pool
 no cdp enable
 ppp authentication chap pap dialin
 group-range 65 88
!
interface Group-Async2
 ip unnumbered Loopback0
 encapsulation ppp
 async mode interactive
 peer default ip address pool dialin_pool
 no cdp enable
 ppp authentication chap pap dialin
 group-range 97 120
!
interface Dialer0
 ip unnumbered Loopback0
 no ip mroute-cache
 encapsulation ppp
 peer default ip address pool dialin_pool
 dialer in-band
 dialer-group 1
 no fair-queue
 no cdp enable
 ppp authentication chap pap dialin
 ppp multilink
!
router eigrp 10
 network 10.0.0.0
 passive-interface Dialer0
 no auto-summary
!
ip local pool dialin_pool 10.1.2.1 10.1.2.50
ip default-gateway 10.1.1.1
ip classless
!
dialer-list 1 protocol ip permit
!
line con 0
 login authentication console
line 65 88
 autoselect ppp
 autoselect during-login
 login authentication dialin
 modem DialIn
line 97 120
 autoselect ppp
 autoselect during-login
 login authentication dialin
 modem DialIn
line aux 0
 login authentication console
line vty 0 4
 login authentication vty
 transport input telnet rlogin
!
end