Cisco Systems CP6921CK9 manual General Troubleshooting Tips, Checking Power Connection

Chapter 9 Troubleshooting and Maintenance

General Troubleshooting Tips

Step 4 From Cisco Unified Communications Manager, choose System > Server and verify that the server is referred to by its IP address and not by its DNS name.

Step 5 From Cisco Unified Communications Manager, choose Device > Phone > Find and verify that you have assigned the correct MAC address to this Cisco Unified IP Phone. For information about determining a MAC address, see the “Determining the MAC Address for a Cisco Unified IP Phone” section on page 2-10.

Step 6 Power cycle the phone.

Checking Power Connection

In most cases, a phone will restart if it powers up by using external power but loses that connection and switches to PoE. Similarly, a phone may restart if it powers up by using PoE and then gets connected to an external power supply.

General Troubleshooting Tips

Table 9-1provides general troubleshooting information for the Cisco Unified IP Phone.

Table 9-1	Cisco Unified IP Phone Troubleshooting
Summary			Explanation
Connecting a Cisco Unified IP Phone to			Cisco does not support connecting an IP phone to another IP phone through the
another Cisco Unified IP Phone/			PC port. Each IP phone should directly connect to a switch port. If phones are
			connected together in a line (by using the PC port), the phones will not work.
Poor quality when calling digital cell			In Cisco Unified Communications Manager, you can configure the network to
phones using the G.729 protocol.			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			A prolonged Layer 2 broadcast storm (lasting several minutes) on the voice
IP phones to reset, or be unable to make or			VLAN may cause IP phones to reset, lose an active call, or be unable to initiate
answer a call.		or answer a call. Phones may not come up until a broadcast storm ends.
Moving a network connection from the			If you are powering your phone through the network connection, you must be
phone to a workstation.			careful if you decide to unplug the phone’s network connection and plug the
			cable into a desktop computer.
			Caution	The computer’s 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.

Cisco Unified IP Phone 6921, 6941, and 6961 Administration Guide for Cisco Unified Communications Manager 7.1 (SCCP)

9-8 OL-19025-01