A dial pan allows people to call each other by dialing a number on the telephone, Dial plans inculde access codes, area codes and specialized codes.The North American Public Switched Telephone network uses a ten-digit plan thant includes a three-digit area code and a seven-digit telephone number (that is :904-555-4568),Most plans must comply with the telephone networkd to which they connect, Dial plans are similary 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 connections, Dial peers are a cirtical component of VoIP.
1 Types of Dial Peers
The First basic command required to conigure 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 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
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dial-peer voice 3 pots<--- POTS dial peer
destination-pattern 5556123
port 2/0/1
dial-peer voice 4 voip<----VoIP dila peer
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
--->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 the VoIP dial peers are configured useing 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 remote router or device.
2 Destination Patterns
Another command used with dial peers is destionation-pattern,
the destination pattern is used to associate a dial string with a particaular telephony device, The call is routed when a dialed string matches a destination pattern, the POST or VoIP voice port configuation 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 . reprsents a single telephone nuimber digit ,If a destination pattern were configured as destiantion-pattern 28674.., a telephone number starting with 28674 and ending with any two additional digits would be routed through this port
dial-peer voice 3 pots<--- POTS dial peer
destination-pattern 5556123<---Destination pattern
port 2/0/1
dial-peer voice 4 voip<----VoIP dila peer
destination-pattern 5557000<---<---Destination pattern
session target ipv4:12.91.0.1
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3 Ports and Session Targets
other important commands used to configure dial peers include the port and session command.
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 sampel configurations provide basic examples of the port and session commands for POTS and VoIP 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 2 pots
destination-pattern 5556123
port 2/0/1 --->port
dial-peer voice 4 voip
destiantion-pattern 5557000
session target ipv4:12.91.0.1-->Session
4 Call Legs
A call leg is a logical connection 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 peer must be configurated for each call leg to complete the path .
The basic configuration for POTS and VoIP dial peers
dial-peer voice 3 pots
destination-pattern 5556123
port 2/0/1
dial-peer voice 4 voip
destiantion-pattern 5557000
session target ipv4:12.91.0.1
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