Cisco MC3810 Multiservice Concentrator Configuration Guide
Configuring Voice over HDLC
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Table Of Contents

Configuring Voice over HDLC

Configuring HDLC Voice Encapsulation

Configuring Dial Peers

Configuring POTS Dial Peers

Configuring VoHDLC Dial Peers

VoHDLC Configuration Example


Configuring Voice over HDLC

Caution Beginning with Cisco IOS Releases 12.0(7)XK and 12.1(2)T, this feature is no longer supported.

This chapter describes how to configure a Cisco MC3810 multiservice access concentrator for Voice over High-Level Data Link Control (VoHDLC), a protocol that provides Cisco serial encapsulation.

VoHDLC enables a Cisco MC3810 to carry live voice traffic (for example, telephone calls and faxes) back-to-back to a second Cisco MC3810. VoHDLC on the Cisco MC3810 is supported on serial ports 0 or 1, or on 0:x (the T1/E1 trunk, where x represents the channel group number).

This chapter is organized as follows:

•Configuring HDLC Voice Encapsulation

•Configuring Dial Peers

•VoHDLC Configuration Example

Configuring VoHDLC is simpler than configuring VoFR or VoATM. Because the target voice-network peer is another Cisco MC3810 configured back-to-back with the first Cisco MC3810, you do not have to configure the network backbone to support VoHDLC.

Configuring HDLC Voice Encapsulation

Before you can configure HDLC dial peers, you need to configure the HDLC voice encapsulation.

To configure HDLC voice encapsulation, complete the following steps in global configuration mode:

Step
Command
Purpose
1 
router(config)# controller  
{t1 | e1} number

If you will configure VoHDLC over the T1/E1 trunk, enter controller configuration mode.

If you will configure VoHDLC over serial port 0 or 1, proceed to step 4.

The number should be 1 if the controller is for the interface to the local phone device or PBX (through the DVM). The number should be 0 for the interface to the WAN (through the MFT).

2 

router(config-controller)# 
tdm-group tdm-group-no timeslot 
timeslot-list

Configure a time-division multiplexing (TDM) channel group for the controller.

3 

router(config)# interface serial 
0:x point-to-point

If configuring VoHDLC over the T1/E1 trunk, enter interface configuration mode by specifying serial 0:x, where x is the channel group number.

Note In Cisco IOS Release 11.3(1) MA, serial port 2 was a valid port number. Beginning with Release 12.0, serial 2 is not a valid designation on the Cisco MC3810.

Proceed to step 5.

4 
router(config)# interface serial 
number point-to-point

If configuring VoHDLC over a serial port, enter interface configuration mode and configure serial interface 0 or 1.

5 
router(config-if)# voice-encap 
size

Configure the voice segmentation size. The valid range for the size value is from 80-1600. There is no default.


Proceed to the next section, "Configuring Dial Peers."

Configuring Dial Peers

Dial peers describe the entities to and/or from which a call is established. Dial-peer configuration tasks define the address or set of addresses serviced by that dial peer and the call parameters required to establish a call to and/or from that dial peer.

There are two different kinds of dial peers:

•Plain old telephone service (POTS)—Dial peer connected via a traditional telephony network. POTS dial peers point to a particular voice-port on a voice network device.

•High-Level Data Link Control (HDLC) dial peer—Dial peer connected back-to-back with the Cisco MC3810. HDLC peers point to specific voice-network devices, normally a second Cisco MC3810.

Note The configuration for HDLC dial peers is very similar to the dial-peer configuration for Frame Relay or ATM. The term HDLC dial peer is used here because in most cases, the peer is back-to-back and normally on the same network.

POTS dial peers associate a telephone number with a particular voice port so that incoming calls for that telephone number can be received and outgoing calls can be placed. HDLC peers point to specific voice-network devices so that incoming calls can be received and outgoing calls can be placed. Both POTS and HDLC dial peers are needed to establish VoHDLC connections if you want to both send and receive calls. Establishing two-way communication using VoHDLC requires establishing a specific voice connection between two defined endpoints.

The following sections describe how to configure POTS and VoHDLC dial peers.

Configuring POTS Dial Peers

To configure a POTS dial peer, you need to uniquely identify the peer (by assigning it a unique tag number), define its telephone number, and associate it with a voice port through which calls will be established. Under most circumstances, the default values for the remaining dial-peer configuration commands will be sufficient to establish connections.

Depending on your dial plan configuration, you may 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. For more information on these topics, see "Voice Dial Plan Considerations."

To configure POTS dial peers, complete the following steps from global configuration mode:

Step
Command
Purpose
1 
router(config)# dial-peer voice 
tag pots

Define a POTS dial peer and enter 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 tag value identifies the dial peer and must be unique on the Cisco MC3810. Do not duplicate a specific tag number.

2 
router(config-dialpeer)# 
destination-pattern string

Configure the dial peer's destination pattern.

The string is a series of digits that specify the E.164 or private dialing plan telephone number. Valid entries are the digits 0-9 and the letters A-D. The following special characters can be entered in the string:

•The star character (*) and the pound sign (#) that appear on standard touch-tone dial pads can be used in any dial string. However, these characters cannot be used as leading characters in a string (for example, *650).

•The period (.) can be entered any time, and is used as a wildcard character. For more information see the "Destination Pattern Wildcards" section.

•The comma (,) can be used only in prefixes, and is used to insert a one-second pause or a delay.

•The timer (T) character can be used to configure variable-length dial plans. For more information, see the "Variable-Length Dial Plans" section.

The plus symbol (+) is not a valid character in the string.

3 
router(config-dialpeer)# port 
slot/port

Associate this POTS dial peer with a specific logical dial interface. Enter the slot/port number of the voice port connected to the POTS dial peer.

4 
router(config-dialpeer)# 
forward-digits {num-digit | all 
| implicit}

(Optional) If using the forward-digits feature, configure the digit-forwarding method that will be used on the dial peer. The valid range for the number of digits forwarded (num-digit) is from 0-32.

The default value is implicit, in which the exactly matched digits are not forwarded. Only digits matched by the wildcard pattern are forwarded.

For more information about the forward-digits functionality, see the "Forward Digits and Voice Default Routes" section.

5 
router(config-dialpeer)# prefix 
string

(Optional) If the forward-digits feature was not configured in the last step, assign the dialed digits prefix for the dial peer.


To configure the next POTS dial peer, exit dial-peer configuration mode by entering exit, and repeat the previous steps. To configure the HDLC dial peer, see the next section.

Configuring VoHDLC Dial Peers

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

Depending on your dial plan configuration, you may 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. For more information on these topics, see "Voice Dial Plan Considerations."

To configure VoHDLC dial peers, complete the following steps from global configuration mode:

Step
Command
Purpose
1 
router(config)# dial-peer voice 
tag vohdlc

Define a dial peer for VoHDLC and enter 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 tag value identifies the dial peer and must be unique on the Cisco MC3810. Do not duplicate a specific tag number.

2 
router(config-dialpeer)# 
destination-pattern string

Configure the dial peer's destination pattern. The same restrictions for the string listed in the POTS dial peer configuration also apply to the VoHDLC destination-pattern.

3 
router(config-dialpeer)# session 
target interface 
serial-port-number

Configure the HDLC session target for the dial peer. For the serial-port-number value, enter either 0 and 1.

4 
router(config-dialpeer)# 
preference value

(Optional) Configure a preference for the VoHDLC dial peer. The value is a number from 0-10 where the lower the number, the higher the preference.

5 
router(config-dialpeer)# 
alt-dial string

(Optional) Configure the alternate dial-out string when configuring on-net-to-off-net alternative dialing.


To configure the next HDLC dial peer, exit dial-peer configuration mode by entering exit, and repeat the previous steps.

Verify Your VoHDLC Dial-Peer Configuration

If you have relatively few dial peers configured, you can use the show dial-peer voice command to verify the validity of your dial-peer configuration.

Troubleshooting Tips

If you are having trouble connecting a call, you can try to resolve the problem by performing the following tasks:

•If you suspect the problem is associated with the dial-peer configuration, use the show dial-peer voice command on the local and remote concentrators to verify that the data is configured correctly on both.

•Toggle the voice port and/or serial port by entering shutdown, and then no shutdown.

VoHDLC Configuration Example

Figure 8-1 shows an example of a simple back-to-back VoHDLC configuration.

Figure 8-1 VoHDLC Configuration Example

The following examples show the configuration for both Cisco MC3810 concentrators to configure back-to-back VoHDLC.

Cisco MC3810 No. 1 

interface Serial1 point-to-point

 ip address 5.5.5.1 255.0.0.0

 no keepalive

 ipx network 2222

 ipx accounting

 voice-encap 512

 clockrate 64000


ip classless


line con 0

 exec-timeout 0 0

line aux 0

line vty 0 4

 login



voice-port 1/1


 dial-peer voice 1 pots

 destination-pattern 3388801

 port 1/1


dial-peer voice 2 pots

 destination-pattern 3388802

 port 1/2

dial-peer voice 44 vohdlc

 destination-pattern 348....

 session target Serial1


end

Cisco MC3810 No. 2 

interface Serial1 point-to-point

 ip address 5.5.5.2 255.0.0.0

 no keepalive

 ipx network 2222

 ipx accounting

 voice-encap 512

 clockrate 64000


ip classless


line con 0

 exec-timeout 0 0

line aux 0

line vty 0 4

 login



voice-port 1/1


 dial-peer voice 1 pots

 destination-pattern 3488803

 port 1/1


dial-peer voice 2 pots

 destination-pattern 3488804

 port 1/2


dial-peer voice 40 vohdlc

 destination-pattern 338....

 session target Serial1


end