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The following table provides general troubleshooting information for the Cisco IP Phone.
Summary |
Explanation |
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Connecting a Cisco IP Phone to another Cisco IP Phone |
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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. |
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Moving a network connection from the phone to a workstation |
If you power your phone through the network connection, you must be careful if you decide to unplug the network connection of the phone and plug the cable into a desktop computer.
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Changing the telephone configuration |
By default, the administrator password settings are locked to prevent users from making changes that could impact their network connectivity. You must unlock the administrator password settings before you can configure them.
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Codec mismatch between the phone and another device |
The RxType and the TxType statistics show the codec that is used for a conversation between this Cisco IP Phone and the other device. The values of these statistics should match. If they do not, verify that the other device can handle the codec conversation, or that a transcoder is in place to handle the service. See Display Call Statistics Window for details. |
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Sound sample mismatch between the phone and another device |
The RxSize and the TxSize statistics show the size of the voice packets that are used in a conversation between this Cisco IP Phone and the other device. The values of these statistics should match. See Display Call Statistics Window for details. |
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Loopback condition |
A loopback condition can occur when the following conditions are met:
In this case, the switch port on the phone can become disabled and the following message appears in the switch console log: HALF_DUX_COLLISION_EXCEED_THRESHOLD To resolve this problem, reenable the port from the switch. |
After you install a phone into your network and add it to Cisco Unified Communications Manager, the phone should start up as described in the related topic below.
If the phone does not start up properly, see the following sections for troubleshooting information.
When you connect a Cisco IP Phone to the network port, the phone does not go through the normal startup process as described in the related topic and the phone screen does not display information.
If the phone does not go through the startup process, the cause may be faulty cables, bad connections, network outages, lack of power, or the phone may not be functional.
To determine whether the phone is functional, use the following suggestions to eliminate other potential problems.
Verify that the network port is functional:
Exchange the Ethernet cables with cables that you know are functional.
Disconnect a functioning Cisco IP Phone from another port and connect it to this network port to verify that the port is active.
Connect the Cisco IP Phone that does not start up to a different network port that is known to be good.
Connect the Cisco IP Phone that does not start up directly to the port on the switch, eliminating the patch panel connection in the office.
Verify that the phone is receiving power:
If the phone still does not start up properly, power up the phone with the handset off-hook. When the phone is powered up in this way, it attempts to launch a backup software image.
If the phone still does not start up properly, perform a factory reset of the phone.
After you attempt these solutions, if the phone screen on the Cisco IP Phone does not display any characters after at least five minutes, contact a Cisco technical support representative for additional assistance.
While the phone cycles through the startup process, you can access status messages that might provide you with information about the cause of a problem. See the "Display Status Messages Window" section for instructions about accessing status messages and for a list of potential errors, their explanations, and their solutions.
If you use DNS to access the TFTP server or Third-Party Call Control Manager, you must ensure that you specify a DNS server.
If you continue to have problems with a particular phone that other suggestions in this chapter do not resolve, the configuration file may be corrupted.
Get a new configuration file remotely from the provisioning server using resync.
If a phone cannot obtain an IP address when it starts up, the phone may not be on the same network or VLAN as the DHCP server, or the switch port to which the phone connects may be disabled.
Ensure that the network or VLAN to which the phone connects has access to the DHCP server, and ensure that the switch port is enabled.
If users report that their phones are resetting during calls or while the phones are idle on their desk, you should investigate the cause. If the network connection and Third Party Call Control connection are stable, a Cisco IP Phone should not reset.
Typically, a phone resets if it has problems in connecting to the Ethernet network or to Third Party Call Control.
Intermittent network outages affect data and voice traffic differently. Your network might be experiencing intermittent outages without detection. If so, data traffic can resend lost packets and verify that packets are received and transmitted. However, voice traffic cannot recapture lost packets. Rather than retransmitting a lost network connection, the phone resets and attempts to reconnect to the network. Contact the system administrator for information on known problems in the voice network.
Verify that you have properly configured the phone to use DHCP. Verify that the DHCP server is set up properly. Verify the DHCP lease duration. We recommend that you set the lease duration to 8 days.
The static IP address assigned to the phone may be incorrect.
If the phone is assigned a static IP address, verify that you have entered the correct settings.
If the phone appears to reset during heavy network usage, it is likely that you do not have a voice VLAN configured.
Isolating the phones on a separate auxiliary VLAN increases the quality of the voice traffic.
In most cases, a phone restarts 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 connects to an external power supply.
Verify that the Ethernet connection to which the Cisco IP Phone connects is up. For example, check whether the particular port or switch to which the phone connects is down and that the switch is not rebooting. Also ensure that no cable breaks exist.
The following sections describe how to resolve audio problems.
When at least one person in a call does not receive audio, IP connectivity between phones is not established. Check the configuration of routers and switches to ensure that IP connectivity is properly configured.
Check the AvgJtr and the MaxJtr statistics. A large variance between these statistics might indicate a problem with jitter on the network or periodic high rates of network activity.
The following sections help troubleshoot general telephone call problems.
The phone does not have a DHCP IP address. The phones display the message Configuring IP or Registering.
The user complains that numbers are missed or delayed when the keypad is used.
Pressing the keys too quickly can result in missed or delayed digits.
If you are working with Cisco TAC to troubleshoot a problem, they typically require the logs from the Problem Reporting Tool to help resolve the issue. You can generate PRT logs using the Configuration Utlility and upload them to a remote log server.
These procedures can be used to identify and correct problems.
Step 1 | On the phone, press Settings. |
Step 2 | Check the DHCP server field. Check the DHCP option for enabled or disabled. |
Step 3 | Check the IP
Address, Subnet Mask, and Default Router fields. If you assign a static IP address to the phone, you must manually enter settings for these options. |
Step 4 | If you are
using DHCP, check the IP addresses that your DHCP server distributes.
See the Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks document, available at this URL: https://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a00800f0804.shtml |
If you have additional questions about troubleshooting your phone, go to the following Cisco website and navigate to the desired phone model: