Chapter 4: Dial Plans and Dial Peers

Cisco Press

A dial plan allows people to call each other by dialing a number on the telephone. Dial plans include access codes, area codes, and specialized codes. The North American Public Switched Telephone Network (PSTN) uses a ten-digit dial plan that includes a three-digit area code and a seven-digit telephone number (that is, 904-555-4568). Most private branch exchanges (PBXs) support variable-length dial plans that use 3 to 11 digits. Dial plans must comply with the telephone networks to which they connect. Dial plans are similar to IP addressing in that only totally private voice networks that are not linked to the PSTN or to other PBXs can use any dial plan they choose.

Dial peers are used to configure dial plans and to identify call source and destination endpoints. They also define each call leg in the call connection. Dial peers are a critical component of VoIP.

Types of Dial Peers

The first basic command required to configure dial peers is dial-peer. The two types of dial peers used in these labs are Plain Old Telephone System (POTS) and voice over IP (VoIP) dial peers. Other dial peer options are multimedia over IP (MMoIP), voice over ATM (VoATM), and voice over Frame Relay (VoFR). The following examples show basic configurations for POTS and VoIP dial peers:

dial-peer voice 3 pots
 destination-pattern 5556123
 port 2/0/1

dial-peer voice 4 voip
 destination-pattern 5557000
 session target ipv4:12.91.0.1

The POTS dial peer maps a dial string to a voice port on a local router or gateway. A dial peer is configured using the dial-peer voice tag {pots | vofr | voip} command. The tag is a number between 1 and 2147483647 that identifies an individual dial peer. POTS dial peers are configured using the dial-peer voice tag pots command, and VoIP dial peers are configured using the dial-peer voice tag voip command. In most cases, POTS dial peers are used to connect a physical voice port to a PBX, a telephone, or the PSTN. VoIP a dial peers are used to define packet voice network attributes and map dial strings to a remote router or device. The following sample configurations provide basic examples of POTS and VoIP dial peers. The first example is a POTS dial peer, and the second is a VoIP dial peer.

dial-peer voice 3 pots <--POTS dial peer
 destination-pattern 5556123
 port 2/0/1

dial-peer voice 4 voip <--VoIP dial peer
 destination-pattern 5557000
 session target ipv4:12.91.0.1

Destination Patterns

Another command used with dial peers is destination-pattern. The destination pattern is used to associate a dial string with a particular telephony device. The call is routed when a dialed string matches a destination pattern. The POTS or VoIP voice port configuration determines the way the call is routed.

To provide flexibility in the configuration, a destination pattern can be either an entire telephone number or a partial number using wildcard digits. For example, a wildcard period character (.) represents a single telephone number digit. If a destination pattern were configured as destination-pattern 28674.., a telephone number starting with 28674 and ending with any two additional digits would be routed through this port.

Several wildcards are destination wildcards. These additional wildcards provide for a more granular configuration. To keep the labs at a basic level, only a few wildcards are discussed and used in these labs. The following sample configurations provide basic examples of destination patterns for POTS and VoIP dial peers. The first example is a destination pattern for a POTS dial peer, and the second is a destination pattern for a VoIP dial peer.

dial-peer voice 3 pots
 destination-pattern 5556123 <--Destination pattern
 port 2/0/1

dial-peer voice 4 voip
 destination-pattern 5557000 <--Destination pattern
 session target ipv4:12.91.0.1

Ports and Session Targets

Other important commands used to configure dial peers include the port and session commands. A port is configured using the port voice interface slot command. The port command associates a dial peer to a physical router port. When a call matches the destination pattern, the call is routed using the port defined with the port command.

The session command associates a dial peer to a network IP address of a remote router or device through which the call should be routed. The session command is used with a VoIP dial peer. When the call matches the destination pattern, the call is sent in the direction of the target IP address defined with the session command. The following sample configurations provide basic examples of the port and session commands for POTS and VoIP dial peers. The first example is a port configuration for a POTS dial peer, and the second is a session target configuration for a VoIP dial peer.

dial-peer voice 3 pots
 destination-pattern 5556123
 port 2/0/1 <--Port

dial-peer voice 4 voip
 destination-pattern 5557000
 session target ipv4:12.91.0.1 <--Session

Call Legs

A call leg is a logical connection (segment) between two routers or between a router and a telephony-capable device. A typical voice call might be composed of four call legs—two from the perspective of the originating router and two from the standpoint of the terminating router. Similar to static routes, dial peers must be configured for each call leg to complete the path.

The following examples show basic configurations for POTS and VoIP dial peers:

dial-peer voice 3 pots
 destination-pattern 5556123
 port 2/0/1

dial-peer voice 4 voip
 destination-pattern 5557000
 session target ipv4:12.91.0.1

Figure 4-1 illustrates a basic voice topology with PBXs and routers; it also shows the concept of call legs. A phone attached to PBX A places a call destined for a phone attached to PBX B. PBX A forwards the call to Router A using a POTS dial peer. Router A forwards the call to Router B using a VoIP dial peer. Router B forwards the call to PBX B using a POTS dial peer. PBX B connects the call to the destination phone.

Figure 4-1

Figure 4-1

Dial Peer Call Legs

Lab 4-1: Single-Router Dial Peer Exercise

In this lab, the company OCSIC.org has decided to train its IT staff on dial peers in a single-router network.

Dial peers are used to forward calls to the destination telephony device. This lab exercise involves a single router with multiple POTS dial peers. It gives you a basic understanding of the POTS dial peer configuration.

This lab exercise provides practice scenarios with POTS dial peer concepts related to a single router.

The objective of this lab is to use the information provided in Figure 4-2 to complete Table 4-1.

You do not need equipment to perform this lab.

The procedure for this lab consists of one task: using the information found in Figure 4-2 to complete Table 4-1.


Note - The configuration in this figure is for instructional purposes only; it might not be appropriate for a production network. Some voice network devices were removed to simplify the figure.


Figure 4-2 illustrates the topology for this lab.

Figure 4-2

Figure 4-2

Lab Topology: A Basic Cisco Dial Plan with a Single Router

Complete Table 4-1 based on the information in Figure 4-2.

Table 4-1 Dial Peer Configuration Table for a Single-Router Network

Click to view table data

Lab 4-2: Single-Router Wildcard Dial Peer Exercise

In this lab, OCSIC.org has decided to train its IT staff on wildcard dial peers in a single-router network.

Wildcard digits work in conjunction with dial peers to provide a more granular method of defining the destination pattern. This lab exercise uses a single router with multiple POTS dial peers. It gives you a basic understanding of wildcard digits.

This lab exercise provides practice scenarios with POTS dial peer wildcard concepts related to a single router.

The objective of this lab is to use the information provided in Table 4-2 and Figure 4-3 to complete Table 4-3.

You do not need equipment to perform this lab.

Destination Pattern Wildcard Digits

The destination pattern can be either a complete telephone number or a partial telephone number with wildcard digits, represented by the period (.) character. Each period represents a wildcard for a single digit that the originating router expects to match. For example, if the destination pattern for a dial peer is defined as 4701..., any dialed string beginning with 4701, plus any three additional digits, matches this dial peer.

In addition to the period, several other symbols are available to be used as wildcard characters in the destination pattern; some of them are provided in Table 4-2. For a complete list of destination wildcards, refer to the Cisco IOS Voice Command PDF at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tvr/vrht_d1.pdf. These symbols are used to minimize the number of dial peers required in configuring telephone number ranges. Some wildcard symbols have been omitted from Table 4-2 and the labs. Dial plans can be complicated; the purpose of these labs is to provide basic configuration examples.

Table 4-2 Common Wildcard Symbols Used in Destination Patterns

SymbolDescription
.The period indicates a single-digit placeholder. For example, 5551... (three periods) matches any dialed string beginning with 5551, plus three additional digits—555100, 555129, 555678, and so on.
[ ]Brackets contain a range of digits. A consecutive range is indicated with a hyphen (-). For example, [1-5] indicates that the digits 1, 2, 3, 4, and 5 will be accepted. A nonconsecutive range is indicated with a comma (,). For example, [2,6] indicates that 2 or 6 will be accepted as dialed digits. Hyphens and commas can be used in combination. For example, [5-7,9] indicates that 5, 6, 7, and 9 will be accepted as dialed digits. Multiple brackets can be used within the same destination pattern.
 Note that only single-digit ranges are supported within destination patterns. For example, [43-207] is invalid.
TIndicates the interdigit timeout value. The router waits a specified time to collect additional dialed digits.

Note - The configuration in Figure 4-3 is for instructional purposes only; it might not be appropriate for a production network. Some voice network devices were removed to simplify the figure.


Figure 4-3 illustrates the topology for this lab.

Figure 4-3

Figure 4-3

Lab Topology: A Cisco Dial Plan with a Single Router

Complete Table 4-3 based on the information in Table 4-2 and Figure 4-3.

Table 4-3 Dial Peer Configuration Table for a Single-Router Network

Click to view table data

Lab 4-3: Two-Router Wildcard Dial Peer Exercise

In this lab, OCSIC.org has decided to train its IT staff on wildcard dial peers in a two-router network.

This lab exercise involves two routers with multiple POTS and VoIP dial peers. It gives you a basic understanding of voice dial peer configuration using wildcard digits.

This lab exercise provides practice scenarios for POTS and VoIP dial peer concepts related to a two-router network using wildcard digits.

The objective of this lab is to use the information provided in Figure 4-4 to complete Table 4-4.

You do not need equipment to perform this lab.


Note - The configuration in this figure is for instructional purposes only; it might not be appropriate for a production network. Some voice network devices were removed to simplify the figure.


Figure 4-4 illustrates the topology for this lab.

Figure 4-4

Figure 4-4

Lab Topology: A Cisco Dial Plan with a Two-Router Network Using Wildcards

Complete Table 4-4 based on the information in Figure 4-4.

Table 4-4 Dial Peer Configuration Table for a Two-Router Network Using Wildcards

Click to view table data

Lab 4-4: Four-Router Wildcard Dial Peer Exercise

In this lab, OCSIC.org has decided to train its IT staff on wildcard dial peers in a four-router network.

This lab exercise involves four routers with multiple POTS and VoIP dial peers. It gives you a basic understanding of voice dial peer configuration using wildcard digits.

This lab exercise provides practice scenarios for POTS and VoIP dial peer concepts related to a four-router network using wildcard digits.

The objective of this lab is to use the information provided in Figure 4-5 to complete Table 4-2.

You do not need equipment to perform this lab.


Note - The configuration in this figure is for instructional purposes only; it might not be appropriate for a production network. Some voice network devices were removed to simplify the figure.


Figure 4-5 illustrates the topology for this lab.

Figure 4-5

Figure 4-5

Lab Topology: A Cisco Dial Plan with a Four-Router Network Using Wildcards

Complete Table 4-5 based on the information in Figure 4-5.

Table 4-5 Dial Peer Configuration Table for a Complex Four-Router Network

Click to view table data

4-5: Complex Two-Router Wildcard Dial Peer Exercise

In this lab, OCSIC.org has decided to train its IT staff on wildcard dial peers in a two-router complex network.

This lab exercise uses two routers in a more-complex topology with multiple POTS and VoIP dial peers. It gives you a basic understanding of voice dial peer configuration using wildcard digits.

This lab exercise provides practice scenarios for POTS and VoIP dial peer concepts related to a complex two-router network using wildcard digits.

The objective of this lab is to use the information provided in Figure 4-6 and Table 4-6 to complete Table 4-7.

You do not need equipment to perform this lab.


Note - The configuration in this figure is for instructional purposes only; it might not be appropriate for a production network. Some voice network devices were removed to simplify the figure.


Figure 4-6 illustrates the topology for this lab.

Figure 4-6

Figure 4-6

Lab Topology: A Cisco Dial Plan with a Complex Two-Router Network Using Wildcards

Table 4-6 shows the dial plan extension numbers associated with the phone ports that you need to know to complete Table 4-7.

Table 4-6 Dial Plan Extension Numbers

PhoneExtensions Associated with the Phone Port
11000, 1001, 1002, 1003, 1004
21015, 1016, 1017, 1019
31321, 1322, 1323, 1327, 1328
41324, 1325, 1326
51008
61200 through 1299
71400, 1401, 1402, 1403, 1404
81405, 1406, 1407, 1409, 1415, 1416, 1417, 1419
91521, 1522, 1523, 1527, 1528
101610 through 1655
111408, 1410
121656 through 1659

Complete Table 4-7 based on the information in Figure 4-6 and Table 4-6.

Table 4-7 Dial Peer Configuration Table: Complex Two-Router Wildcard Dial Peer Exercise

PhonePhone CharacteristicWrite the three basic router configuration lines for each phone using Figure 4-6 and Table 4-6 as a reference.
1Dial peerdial-peer voice 1 pots
Destination patterndestination-pattern 100[0-4]
Portport 2/0
2Dial peer 
Destination pattern 
Port 
3Dial peer 
Destination pattern 
Port 
4Dial peer 
Destination pattern 
Port 
5Dial peer 
Destination pattern 
Port 
6Dial peer 
Destination pattern 
Port 
7Dial peer 
Destination pattern 
Port 
8Dial peer 
Destination pattern 
Port 
9Dial peer 
Destination pattern 
Port 
10Dial peer 
Destination pattern 
Port 
11Dial peer 
Destination pattern 
Port 
12Dial peer 
Destination pattern 
Port 
RouterRouter CharacteristicWrite the three basic router configuration lines to allow the routers to forward calls between the two networks. Use Figure 4-6 and Table 4-6 as a reference.
A to BDial peer 
Destination patter 
Port 
B to ADial peer 
Destination pattern 
Port 

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