14
Cisco 1751 Voice-over-IP Quick Start Guide
78-11259-05
Configuring Voice-over-IP
Dial Plan
Use a dial plan to map the destination telephone numbers with the voice ports on the router. In North
America, the North American Numbering Plan (NANP) is used, which consists of an area code, an office
code, and a station code. Area codes are assigned geographically, office codes are assigned to specific
switches, and station codes identify a specific port on that switch. The format in North America is
1Nxx-Nxx-xxxx, with N = digits 2 through 9 and x = digits 0 through 9. Internationally, each country is
assigned a one- to three-digit country code; the country’s dialing plan follows the country code.
In corporate environments, VoIP can be configured to recognize extension numbers and expand them
into their full E.164 dialed number by using two commands in tandem:
destination-pattern
and
num-exp
. Before you configure these two commands, map individual telephone extensions with their
full E.164 dialed numbers. This can be done easily by creating a number expansion table.
For Cisco voice implementations, two types of dial peers are used to match a dialed number to either a
local telephony port or a remote IP address:
•
POTS dial peer associates a physical voice port with a local telephone device, and the key commands
you need to configure are the
port
and
destination-pattern
commands as shown in the following
example:
West(config)#
dial-peer voice 401 pots
West(config-dial-peer)#
destination-pattern 14085553737
West(config-dial-peer)#
port 0/0
The
destination-pattern
command defines the telephone number associated with the POTS dial
peer. The
port
command associates the POTS dial peer with a specific logical dial interface,
normally the voice port connecting your router to the local POTS network.
•
VoIP dial peer associates a telephone number with an IP address, and the key commands you need
to configure are the
destination-pattern
and
session target
commands as shown in the following
example:
West(config)#
dial-peer voice 501 voip
West(config-dial-peer)#
destination-pattern 1919555....
West(config-dial-peer)#
session target ipv4:192.168.11.3
The
destination-pattern
command defines the telephone number associated with the VoIP dial peer.
The
session target
command specifies a destination IP address for the VoIP dial peer.
Use the
dial-peer voice
command to define dial peers and change to dial peer configuration mode. To
see an example, refer to the individual sections on configuring FXS, FXO, and E&M interfaces later in
this guide.
Wildcards and Number Expansion
Office PBXs are configured so that a user can dial a local call (within the same PBX) by dialing the
extension only—for instance, the four-digit extension 3737 or the five-digit extension 53737 instead of
the full telephone number, 1 408 555-3737.
You can provide the same shortcut on a VoIP network by using the
number-expansion
(
num-exp
)
command.
East(config)#
num-exp 5.... 1408555....
This command tells the router to expand a particular sequence of dialed numbers into a complete
telephone number (destination pattern) as shown in
Table 5
.
