You can set up a Cisco CME system to provide audio paging using the speakers of your IP phones to broadcast the paging audio output. This feature works in conjunction with IP phones that have a speakerphone mode. Only IP phones that are idle are used to output paging audio. IP phones can still be used to make or receive calls during paging. When the phone is used, it simply drops out of the page.
You can create paging groups or zones that output paging audio only on specific groups of IP phones. You can also combine multiple paging groups to output audio paging to multiple paging groups at the same time.
Using your IP phones to provide an audio paging system can save the additional cost of installing a separate overhead audio paging system. If you already have a conventional overhead audio paging system, you can also use this with Cisco CME. You simply need an available physical voice port on your router that can connect to the paging system. Ear and mouth (E&M) voice ports are the easiest to use because they do not usually require external adapter hardware. Because E&M ports usually come in pairs, you can also use the second E&M port as an input to connect to an external music on hold audio source.
The following sections describe how you can use the Cisco CME paging features.
To configure an IP phone-based paging group, you first set up an ephone-dn entry in your system to act as the pilot number for the paging group. Like most of the special-purpose ephone-dns you create for your Cisco CME system, the paging ephone-dn is not directly bound to any of your IP phones. You don't use this ephone-dn in a button command.
The paging group pilot number is the number you dial from a phone to output audio to the paging group. A sample configuration is shown in Example 5-26. Note that you can dial into a paging group from any phone, including via a VoIP connection. You can also set up speed-dial buttons on your IP phones to dial into the paging number for one-button push-to-page operation.
Example 5-26 Paging Pilot Number Configuration
router#show running-config ephone-dn 14 number 6112 name Sales paging ip 188.8.131.52 port 2000
The paging-dn is set up with a pilot number of 6112. When you make a call to 6112, it is answered by the paging-dn. The audio stream from your phone to the paging-dn is broadcast to all the phones in the paging group for ephone-dn 14 using IP Multicast on address 184.108.40.206 and port 2000.
As soon as you have created your paging-dn, you then create a group of IP phones to include in your paging group, as shown in Example 5-27. You do this using the paging-dn command within the ephone command mode. Set the paging-dn command in the ephone command mode to select the tag number of the ephone-dn that you configured as a paging-dn (14 in this example).
Example 5-27 Paging on IP Phones
router#show running-config ephone 12 mac-address 000d.1234.0efc button 1:1 2:6 paging-dn 14 ephone 15 mac-address 000d.4132.f7e4 button 1:4 2:5 paging-dn 14
With the configuration shown in Example 5-27, when you dial the number 6112 from any phone, the speakerphone on ephones 12 and 15 activates, provided that the phones are idle and the audio from the call is IP Multicast to both phones and output via the speakerphone.
There is no limit on the number of IP phones that can be included in a paging group. There is no specific limit on the number of paging-dns and corresponding paging groups you can create. Each paging group consumes one of the finite number of ephone-dns in your Cisco CME system. You can create individual paging groups for each department in your organization—for example, sales, accounts, and service.
Each IP phone can belong directly to only a single paging group. You can enter only one paging-dn configuration per ephone.
Combining Paging Groups
After you have created the individual paging groups, you can combine up to ten paging groups. You use the paging group command followed by a list of the paging-dn tag numbers you want to include in the group. Example 5-28 shows how two paging groups are combined.
Example 5-28 Using the paging group Command
router#show running-config ephone-dn 14 number 6112 name Sales paging ip 220.127.116.11 port 2000 ephone-dn 16 number 6113 name Accounts paging ip 18.104.22.168 port 2000 ephone-dn 17 number 6120 name Sales&Acccounts paging ip 22.214.171.124 port 2000 paging group 14,16 ephone 12 mac-address 000d.1234.0efc button 1:1 paging-dn 14 ephone 15 mac-address 000d.4132.f7e4 button 1:2 paging-dn 14 ephone 19 mac-address 000d.5678.13f4 button 1:24 paging-dn 15 ephone 21 mac-address 000d.8765.23e5 button 1:27 paging-dn 15
In Example 5-28, you can see that paging-dn in ephone-dn 14 creates the paging group for the sales department with pilot number 6112. This group contains ephones 12 and 15. Ephone-dn 16 creates the paging group for the accounts department with pilot number 6113. This group contains ephones 19 and 21.
The combined paging group is created by ephone-dn 17. It uses the pilot number 6120. This combines the paging groups of paging-dn ephone-dns 14 and 16 by listing the ephone-dn tag values after the paging group command.
When you call the pilot number 6120 for the combined group, all four of the IP phones are used to output the paging audio. Note that each paging-dn uses a different multicast IP address. Using different IP Multicast addresses for each paging group allows you to have simultaneous paging to different groups. In this example, it allows you to have unrelated paging to the sales and accounts department at the same time.
Multicast Routing for Paging
An IP Multicast address is any IP address in the range 126.96.36.199 to 188.8.131.52. However, you cannot use the 224.x.x.x address range, because it is typically reserved, and most Cisco IP phones do not accept IP Multicast streams in this range. For most normal use, the IP Multicast address range 239.x.x.x is recommended. This address range is locally scoped and is not routed outside your network. The details of IP Multicast routing are more formally defined in RFC 1112, Host Extensions for IP Multicasting.
For simple Cisco CME systems where all your IP phones are connected to the same local LAN, you do not need to configure your router(s) for multicast routing to use the Cisco CME paging mechanism. The Cisco CME software takes care of directing multicast packets to the appropriate local Ethernet interface(s) that connect to your IP phones. Because the IP phones maintain SCCP communication with CME over TCP/IP, the Cisco CME router has direct knowledge of the locations of the phones and, therefore, does not need to rely on multicast routing mechanisms to distribute IP Multicast packets. If you have a small number of IP phones that are not directly connected to the Cisco CME router local LAN, you can still include these in paging by configuring individual IP phones to use unicast paging. Add the unicast option to the phone's paging configuration under the ephone command, as shown in Example 5-29.
Example 5-29 Unicast Paging
router#show running-config ephone 12 mac-address 000d.1234.0efc button 1:1 paging-dn 14 unicast
You can have up to ten unique output destinations in a paging audio IP stream, where a destination is either a router interface (Ethernet port) or a phone's unique IP (unicast) address. This means that if the multicast IP audio stream is sent out on only a single Ethernet port for the benefit of the majority of your phones, you may additionally include up to nine nonmulticast phone destinations using individual unicast paging.
For more complex local networks that involve multiple routing hops, you most likely need to configure multicast routing on the routers that are located between the Cisco CME router and your IP phones.