Configuring Voice over IP
VoIP Basics
5
Cisco AS5350XM and Cisco AS5400XM Universal Gateways Software Configuration Guide
Matching Rules
A gateway redirects an incoming call along the most appropriate outbound leg. It chooses the most
appropriate leg by first finding the POTS or VoIP (depending on call direction) dial peer whose
destination pattern matches the call’s dialed digits. For outbound VoIP legs, it chooses the longest
matching dial peer. If more than one such match exists, it checks whether preferences have been assigned
those peers and chooses the peer with the lowest preference level.
Example
Let us say, for a very simple example (your implementation will be far more complex), that a company
has offices in San Jose and Newark. Extensions in the San Jose office are in the range 5000 to 5999, those
in the Newark office in the range 6000 to 6999. A caller at San Jose extension 5000 wants to call Newark
extension 6000.
Table 15
shows the dial peers needed to make this connection:
When the San Jose caller at extension 5000 dials the digits 6000, the originating gateway in San Jose
does the following:
1.
Receives, through port 1/0:1 to which extension 5000 connects, the dialed digits 6000.
2.
Searches its VoIP dial peers until it finds dial-peer 2, whose destination pattern best matches the
dialed digits.
3.
Sends the dialed digits through the IP network to the gateway specified by dial-peer 2’s session
target (172.16.1.1).
The destination gateway in Newark now does the following:
1.
Receives the dialed digits through the IP network.
2.
Searches its POTS dial peers until it finds dial-peer 4, whose destination pattern matches the dialed
digits.
3.
Sends the call out the port specified by that dial peer (port 1/0:3, which connects to extension 6000).
Table 15
Sample Dial Peers
Dial-Peer (Tag)
Number
Dial Peer
Function
San Jose Gateway
1
dial-peer voice 1 pots
destination-pattern 5000
port 1/0:1
Associates San Jose extension 5000 with
San Jose gateway port 1/0:1.
2
dial-peer voice 2 voip
destination-pattern 6...
session target ipv4:172.16.1.1
Transmits San Jose’s Newark-bound calls
(extensions 6000–6999) to the gateway in
Newark whose IP address is 172.16.1.1.
Newark Gateway
3
dial-peer voice 3 voip
destination-pattern 5...
session target ipv4:172.19.1.1
Transmits Newark’s San Jose-bound calls
(extensions 5000–5999) to the gateway in
San Jose whose IP address is 172.19.1.1.
4
dial-peer voice 4 pots
destination-pattern 6000
port 1/0:3
Associates Newark extension 6000 with
Newark gateway port 1/0:3.
