ISDN Configuration Basics

Lab 15a: Configuring Voice over Frame Relay ”Part II

Lab Walkthrough

POTS peers enable incoming calls to be received by a particular telephony device. To configure a POTS peer, you need to uniquely identify the peer (by assigning it a unique tag number), define its telephone number(s), and associate it with a voice port through which calls will be established. In this example, you are using a four-digit dialing plan.

To configure a POTS dial peer, use the commands in Table 6-2 beginning in global configuration mode.

Table 6-2. Steps for Configuring POTS Dial Peers

Step	Command	Purpose
Step 1	Router# configure terminal	Enters global configuration mode.
Step 2	Router(config)# dial-peer voice number pots	Enters dial peer configuration mode and defines a local dial peer that will connect to the POTS network. The number argument is one or more digits identifying the dial peer. Valid entries are from 1 to 2147483647. The pots keyword indicates a peer using basic telephone service.
Step 3	Router(config-dialpeer)# destination-pattern string [T]	Configures the destination pattern of the dial peer so that the system can reconcile dialed digits with a telephone number. The string argument is a series of digits that specify the E.164 or private dialing plan phone number. Valid entries are the numerals 0 through 9 and the letters A through D. The plus symbol (+) is not valid. You can enter the following special characters : The star character (*) that appears on standard touchtone dial pads can be in any dial string but not as a leading character (for example, *650). The period (.) acts as a wildcard character. The comma (,) can be used only in prefixes and inserts a 1-second pause. When the timer (T) character is included at the end of the destination pattern, the system collects dialed digits as they are entered until the interdigit timer expires (10 seconds, by default) or the user dials the termination of the end-of-dialing key (default is #).

To configure a VoFR dial peer, you need to uniquely identify the peer (by assigning it a unique tag number) and define the outgoing serial port number and the virtual circuit number.

Depending on your dial plan configuration, you might need to consider how to configure voice networks with variable-length dial plans, number expansion, excess digit playout, forward digits, and default voice routes, or use hunt groups with dial peer preferences.

If you will be sending switched calls over the Frame Relay network, you must configure the VoFR dial peers to specifically support switched calls.

To configure a VoFR dial peer to support switched calls, use the commands shown in Table 6-3 beginning in global configuration mode.

Table 6-3. Steps for Configuring VoFR Dial Peers to Support Switched Calls

Step	Command	Purpose
Step 1	Router(config)# dial-peer voice number vofr	Defines a VoFR dial peer and enters dial peer configuration mode. All subsequent commands that you enter in dial peer voice mode before you exit will apply to this dial peer. The number value tag identifies the dial peer and must be unique on the router. Do not duplicate a specific tag number.
Step 2	Router(config-dial-peer)# destination-pattern string	Configures the dial peer destination pattern. The same restrictions for the string listed in the POTS dial-peer configuration apply to the VoFR destination pattern.
Step 3	Router(config-dial-peer)# session target interface dlci [ cid ]	Configures the Frame Relay session target for the dial peer.

The physical serial interface, Serial 1/0, is configured to support Frame Relay encapsulation. You also will notice that Frame Relay traffic shaping is configured. Enabling FRTS on an interface enables both traffic shaping and per-VC queuing on all the PVCs and SVCs on the interface. Traffic shaping enables the router to control the output rate of the circuit and react to congestion notification information, if also configured.

The logical interface Serial 1/0.1 is configured as a basic point-to-point subinterface. Again, notice the two additional configuration parameters on this interface: class voice and vofr cisco. To associate a map class with a specified data-link connection identifier (DLCI), use the class virtual circuit configuration command. To remove the association between the DLCI and the map class, use the no form of this command. On the Cisco 2600, 3600, and 7200 series routers, entering the vofr cisco command is the only method for configuring Cisco proprietary voice encapsulation. You must then configure a map class to enable voice traffic on the PVCs.

The map-class frame-relay vofr is just defining a map class named vofr. To specify how much bandwidth should be reserved for voice traffic on a specific DLCI, use the frame-relay voice bandwidth command. To release the bandwidth previously reserved for voice traffic, use the no form of this command.

Example 6-2 defines a Frame Relay map class named voice.

Example 6-2 Defining a Frame Relay Map Class

  map-class frame-relay voice   frame-relay cir 768000   frame-relay bc 1000   frame-relay mincir 120000   no frame-relay adaptive-shaping   frame-relay fair-queue   frame-relay voice bandwidth 78000   frame-relay fragment 1500  

To specify the incoming or outgoing committed information rate (CIR) for a Frame Relay virtual circuit, use the frame-relay cir map class configuration command. To reset the CIR to the default, use the no form of this command.

To specify the incoming or outgoing committed burst size (Bc) in bits for a Frame Relay virtual circuit, use the frame-relay bc map class configuration command. In this example, 1000 bits is used. To reset the committed burst size to the default, use the no form of this command.

To specify the minimum acceptable incoming or outgoing CIR in bits per second for a Frame Relay virtual circuit, use the frame-relay mincir map class configuration command. In this example, 120000 bits is used. To reset the minimum acceptable CIR to the default, use the no form of this command.

To select the type of backward notification that you want to use, use the frame-relay adaptive-shaping map class configuration command. To disable backward notification, use the no form of the command.

To enable weighted fair queuing for one or more Frame Relay PVCs, use the frame-relay fair-queue map class configuration command in conjunction with the map-class frame-relay command. To disable weighted fair queuing for a Frame Relay map class, use the no form of this command.

To specify how much bandwidth should be reserved for voice traffic on a specific DLCI, use the frame-relay voice bandwidth command. To release the bandwidth previously reserved for voice traffic, use the no form of this command.

To enable fragmentation of Frame Relay frames for a Frame Relay map class, use the frame-relay fragment map class configuration command. To disable Frame Relay fragmentation, use the no form of this command. Fragment size specifies the number of payload bytes from the original Frame Relay frame that will go into each fragment. This number excludes the Frame Relay header of the original frame. All the fragments of a Frame Relay frame except the last will have a payload size equal to fragment_size; the last fragment will have a payload less than or equal to fragment_size. Valid values are from 16 to 1600 bytes; the default is 53.

In Example 6-3, the configuration parameters on vofr2 are much the same as those in vofr1, with the exception of the dial peers. The destination patterns are reversed and the dlci information in the session target has been changed to point to the correct dlci.

Example 6-3 Configuring the Voice Ports on vofr2

 Current configuration: ! version 12.0 service timestamps debug uptime service timestamps log uptime no service password-encryption !  hostname vofr2  ! enable password cisco ! ip subnet-zero no ip domain-lookup ! ! ! ! voice-port 3/0/0  timeouts call-disconnect 0 ! voice-port 3/0/1  timeouts call-disconnect 0 ! voice-port 3/1/0  timeouts call-disconnect 0 ! voice-port 3/1/1  timeouts call-disconnect 0 !  dial-peer voice 22 pots   destination-pattern 2222   port 3/0/0   !   dial-peer voice 1111 vofr   destination-pattern 1111   session target Serial1/0 200  ! ! interface Ethernet0/0  no ip address  no ip directed-broadcast  shutdown ! interface TokenRing0/0  no ip address  no ip directed-broadcast  shutdown  ring-speed 16 !  interface Serial1/0   no ip address   no ip directed-broadcast   encapsulation frame-relay   frame-relay traffic-shaping   !   interface Serial1/0.1 point-to-point   ip address 150.150.10.2 255.255.255.0   no ip directed-broadcast   frame-relay interface-dlci 200   class voice   vofr cisco  ! interface Serial1/1  no ip address  no ip directed-broadcast  shutdown ! interface Serial1/2  no ip address  no ip directed-broadcast  shutdown ! interface Serial1/3  no ip address  no ip directed-broadcast  shutdown ! interface FastEthernet2/0  no ip address  no ip directed-broadcast  shutdown ! router igrp 1  network 150.150.0.0 ! ip classless no ip http server ! !  map-class frame-relay vofr   frame-relay voice bandwidth 64000   !   map-class frame-relay voice   frame-relay cir 768000   frame-relay bc 1000   frame-relay mincir 12000   no frame-relay adaptive-shaping   frame-relay fair-queue   frame-relay voice bandwidth 78000   frame-relay fragment 1500  ! ! line con 0  password cisco  transport input none line aux 0  password cisco line vty 0 4  password cisco  login ! end vofr2# 

Now that both router configurations are complete, pick up the phone set on vofr1 and dial the digits 2222. 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 vofr1 and try placing a call from vofr2 by dialing 1111.