Cisco IOS Dial Peers: Trunk Groups

In previous blogs, we have configured a PSTN dial plan using seven POTS dial peers to meet the North American Numbering Plan dial requirements. A customer with a four port FXO interface to the PSTN would be required to configure four sets of these dial peers (i.e. 4 x 7 = 28) to utilize all four available foreign exchange office (FXO) ports. Trunk groups can be configured to bind the VIC2-4FXO voice interfaces to a logical trunk group call routing entity allowing the configuration to be done with only seven dial peers. The configuration of the trunk group is shown below: Trunk group 1 ! Voice-port 0/2/0 Trunk-group 1 ! Voice-port 0/2/1 Trunk-group 1 ! Voice-port 0/2/2 Trunk-group 1 ! Voice-port 0/2/3 Trunk-group 1 ! Dial-peer voice 200 pots Destination-pattern 9[2-8]11 Forward-digits 3 Trunkgroup 1 ! Dial-peer voice 9911 pots Destination-pattern 9911 Forward-digits 3 Trunkgroup 1 ! Dial-peer voice 911 pots Destination-pattern 911 Prefix 911 Trunkgroup 1 ! Dial-peer voice 201 pots Destination-pattern 9[2-9]…… Trunkgroup 1 ! Dial-peer voice 202 pots Destination-pattern 9[2-9]..[2-9]…… Trunkgroup 1 ! Dial-peer voice 203 pots Destination-pattern 91[2-9]..[2-9]…… Prefix 1 Trunkgroup 1 ! Dial-peer voice 204 pots Destination-pattern 9011T Prefix 011 Trunkgroup 1 The trunk group configuration takes care of the outbound dialing requirements to the PSTN for all four FXO interfaces. Since FXO interfaces do not support direct inward dialing, we will not be able to use the dial-peer 1 that was used for inbound call routing with the PRI in previous blogs. All inbound calls will be need to be redirected to an operator or automated attendant server since DID is not supported on the FXO voice interfaces. The following configuration will route all inbound calls to any of the FXO voice interfaces to extension 11000 (automated attendant opening greeting): Voice-port 0/2/0 Connection plar opx 11000 ! Voice-port 0/2/1 Connection plar opx 11000 ! Voice-port 0/2/2 Connection plar opx 11000 ! Voice-port 0/2/3 Connection plar opx 11000 If the connection plar command is used without the opx (off premise extension) option, the inbound call leg will be terminated and the carrier billing record will begin even though the call has been redirected. The connection plar option would also disrupt the ringback cadence the calling party is used to hearing when the FXO port picks up the call. The connection plar opx command cuts through the signaling without terminating the inbound call leg or disrupting ringback cadence to the calling party. Cisco sells analog trunk interfaces that support DID functionality, but the voice interfaces can only be used for inbound call routing. FXO ports do not support DID, but they have the advantage of sending and receiving phone calls. REFERENCES Understanding Foreign Exchange Office (FXO) Voice Interface Cards http://www.cisco.com/en/US/products/hw/routers/ps274/products_tech_note09186a00800b53c7.shtml Cisco IOS Voice Port Configuration Guide http://www.cisco.com/en/US/docs/ios/voice/voiceport/configuration/guide/12_4t/vp_12_4t_book.html