Information Technology Reference
In-Depth Information
As a result, calls into the CME_A router hear a second dial tone played after they dial into
the CME_A router from the PSTN. This is essentially the router saying, “Yes, I received
your call; please tell me what to do now.” If the caller on the phone were to dial 1500, the
CME_A router would forward them to the receptionist. However, the likelihood of a
PSTN caller doing this is slim. This is where PLAR comes to the rescue. Example 6-14 con-
figures two analog FXO ports as PLAR connections for incoming calls.
Example 6-14
FXO PLAR Configuration
CME_A(config)# voice-port 2/0/0
CME_A(config-voiceport)# connection plar 1500
CME_A(config-voiceport)# exit
CME_A(config)# voice-port 2/0/1
CME_A(config-voiceport)# connection plar 1500
CME_A(config-voiceport)# exit
By entering the connection plar 1500 command under both FXO ports, the router re-
ceives incoming calls from the PSTN and immediately forwards them to the receptionist
phone rather than playing a second dial tone.
Note: Configuring PLAR connections for incoming calls is something you only need to
do for analog FXO trunks. Digital PSTN connections (such as T1 or E1) receive DNIS infor-
mation for incoming calls, which the router can use for Direct Inward Dial (DID) services.
Understanding Router Call Processing and Digit
Manipulation
Understanding how the router processes dialed digits is critical to accurately implement-
ing dial peers. There are two primary rules to guide you in your dial peer strategy:
The most specific destination pattern always wins.
Key
To p i c
When a match is found, the router immediately processes the call.
This section presents examples of these rules in action. Example 6-15 shows the dial peers
for a router.
Example 6-15
Sample Dial Peer Configuration 1
dial-peer voice 1 voip
destination-pattern 555[1-3]...
session target ipv4:10.1.1.1
dial-peer voice 2 voip
destination-pattern 5551...
session target ipv4:10.1.1.2
 
 
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