ISDN Labs

Lab 15c: Configuring Voice over ATM ”Part II

Lab Walkthrough

Now, take a look at the configurations that you will use on each of these routers to accomplish your Voice over ATM lab. The configuration of the voice ports, dial peers, and QOS mechanisms is discussed. For the purpose of this lab, the Cisco voice-capable routers have host names of voatm1 and voatm2. Example 6-6 shows the configuration for voatm1.

Example 6-6 Configuring Voice over ATM on voatm1

 Current configuration: ! version 12.1 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname voatm1 ! enable password cisco ! ! ! ! ! ! ces 1/0 ! ip subnet-zero ! lane client flush ! ! ! ! ! controller T1 1/0 ! ! ! interface FastEthernet0/0  no ip address  shutdown  duplex auto  speed auto ! interface FastEthernet0/1  no ip address  shutdown  duplex auto  speed auto !  interface ATM1/0   no ip address   no atm scrambling cell-payload   no atm ilmi-keepalive   pvc 1/150   vbr-rt 128 64 32   encapsulation aal5mux voice  ! ! interface Serial2/0  no ip address  shutdown ! interface Serial2/1  no ip address  shutdown ! interface Serial2/2  no ip address  shutdown ! interface Serial2/3  no ip address  shutdown ! ip classless no ip http server ! ! voice-port 3/0/0 ! voice-port 3/0/1 ! voice-port 3/1/0 ! voice-port 3/1/1 !  dial-peer voice 1 pots   destination-pattern 4444   port 3/0/0   !   dial-peer voice 2 voatm   destination-pattern 1000   session target ATM1/0 pvc 1/150  ! ! line con 0  transport input none line aux 0 line vty 0 4 ! end 

The following is a description of the configuration parameters on the ATM interface.

The no atm scrambling cell-payload randomizes the ATM cell payload frames to avoid continuous nonvariable bit patterns and improve the efficiency of ATM's cell delineation algorithms. Normally, the default setting for this command is sufficient, with no specific command required. By default, scrambling is off for T1 or E1 links.

To enable or disable ILMI connectivity procedures and to change the ILMI keepalive poll interval, use the atm ilmi-keepalive interface configuration command. To disable ILMI connectivity procedures, use the no form of this command. This is disabled by default.

To configure the real-time variable bit rate (VBR) for Voice over ATM connections, use the vbr-rt ATM virtual circuit configuration command. vbr-rt peak-rate average-rate burst. The parameters for the vbr-rt command are described as follows :

• peak-rate ” The peak information rate (PIR) of the voice connection in kbps. The range is 56 to 10000. Peak value: (2 x the maximum number of calls) x 16 kb.

• average-rate ” The average information rate (AIR) of the voice connection in kbps. The range is 1 to 56. Average value: (1 x the maximum number of calls) x 16 kb.

• burst ” Burst size in number of cells . The range is 0 to 65536. Burst value: x 4 the maximum number of calls.

encapsulation aal5mux voice sets the encapsulation of the PVC to support voice traffic.

pvc 1/150 (pvc vpi/vci) creates an ATM PVC for voice traffic and enters virtual circuit configuration mode.

The POTS dial peer is configured the same way as in the VoFR and VoIP labs and is associated with voice port 3/0/0.

The VoATM dial peer is not pointing at an IP address, as it was in the VoIP lab, but now points to an ATM interface and a voice PVC.

Example 6-7 shows the configuration for the second router in your VoATM lab. The configurations are nearly identical with the exception of the atm clock internal configuration parameter on the ATM interface. This means that the transmit clock is generated internally.

Example 6-7 Configuring Voice over ATM on voatm2

 Current configuration: ! version 12.1 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname voatm2 ! enable password cisco ! ! ! ! ! ! ces 1/0 ! ip subnet-zero ! lane client flush ! ! ! ! ! controller T1 1/0 ! ! ! interface FastEthernet0/0  no ip address  shutdown  duplex auto  speed auto ! interface FastEthernet0/1  no ip address  shutdown  duplex auto  speed auto !  interface ATM1/0   no ip address   atm clock INTERNAL   no atm scrambling cell-payload   no atm ilmi-keepalive   pvc 1/150   vbr-rt 128 64 32   encapsulation aal5mux voice  ! ! interface Serial2/0  no ip address  encapsulation frame-relay  shutdown  frame-relay lmi-type cisco ! interface Serial2/1  no ip address  shutdown ! interface Serial2/2  no ip address  shutdown ! interface Serial2/3  no ip address  shutdown ! ip classless no ip http server ! ! voice-port 3/0/0 ! voice-port 3/0/1 ! voice-port 3/1/0 ! voice-port 3/1/1 !  dial-peer voice 1 pots   destination-pattern 1000   port 3/1/0   !   dial-peer voice 2 voatm   destination-pattern 4444   session target ATM1/0 pvc 1/150  ! ! line con 0  transport input none line aux 0 line vty 0 4 ! end 

Now that both router configurations are complete, pick up the phone set on voatm1 and dial the digits 1000. If your configurations are correct and your routers are physically connected as described earlier, you should be able to complete a successful call. Hang up the phone set on voatm1 and try placing a call from voatm2 by dialing 1000.