Cisco 7931G Administration Guide - Page 219
Summary, Explanation, In Cisco Unified Communications Manager, you can con
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Chapter 9 Troubleshooting and Maintenance General Troubleshooting Tips Table 9-2 Cisco Unified IP Phone Troubleshooting Summary Explanation Daisy-chaining IP phones Daisy chaining (connecting an IP phone to another IP phone through the access port) is not supported. Each IP phone should directly connect to a switch port. Poor quality when calling digital cell phones using the G.729 protocol In Cisco Unified Communications Manager, you can configure the network to use the G.729 protocol (the default is G.711). When using G.729, calls between an IP phone and a digital cellular phone will have poor voice quality. Use G.729 only when absolutely necessary. Prolonged broadcast storms cause IP phones to reset, or be unable to make or answer a call A prolonged Layer 2 broadcast storm (lasting several minutes) on the voice VLAN may cause IP phones to reset, lose an active call, or be unable to initiate or answer a call. Phones may not come up until a broadcast storm ends. Moving a network connection from the phone to a workstation If you are powering your phone through the network connection, you must be careful if you decide to unplug the phone's network connection and plug the cable into a desktop computer. Changing the telephone configuration Caution The computer network card cannot receive power through the network connection; if power comes through the connection, the network card can be destroyed. To protect a network card, wait 10 seconds or longer after unplugging the cable from the phone before plugging it into a computer. This delay gives the switch enough time to recognize that there is no longer a phone on the line and to stop providing power to the cable. By default, the network configuration options are locked to prevent users from making changes that could affect their network connectivity. You must unlock the network configuration options before you can configure them. See the "Unlocking and Locking Options" section on page 4-4 for details. Cisco Unified IP Phone 7931G Administration Guide for Cisco Unified Communications Manager 6.0 OL-12457-01 9-15