Troubleshooting

General Troubleshooting Information

The following table provides general troubleshooting information for the Cisco IP Phone.

Table 1 Cisco IP Phone Troubleshooting

Summary

Explanation

Connecting a Cisco IP Phone to another Cisco IP Phone

Cisco does not support connecting an IP phone to another IP Phone through the PC port. Each IP Phone should connect directly to a switch port. If phones are connected together in a line by using the PC port, the phones do not work.

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 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.

Caution   

The network card in the computer 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.

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.

Note    If the administrator password is not set in common phone profile, then user can modify the network settings.

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.

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.

Loopback condition

A loopback condition can occur when the following conditions are met:

  • The SW Port Configuration option on the phone is set to 10 Half (10-BaseT/half duplex).
  • The phone receives power from an external power supply.
  • The phone is powered down (the power supply is disconnected).

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.

Startup Problems

After you install a phone into your network and you can access the phone web page (phone Configuration Utility), 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.

Cisco IP Phone Does Not Go Through the Normal Startup Process

Problem

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.

Cause

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.

Solution

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 you are using external power, verify that the electrical outlet is functional.

    • If you are using in-line power, use the external power supply instead.

    • If you are using the external power supply, switch with a unit that you know to be functional.

  • 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.

Phone Displays Error Messages

Problem

Status messages display errors during startup.

Solution

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.

Phone Cannot Connect Using DNS

Problem

The DNS settings may be incorrect.

Solution

If you use DNS to access the TFTP server or Third-Party Call Control Manager, you must ensure that you specify a DNS server.

Configuration File Corruption

Problem

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.

Solution

Get a new configuration file remotely from the provisioning server using resync.

Cisco IP Phone Cannot Obtain IP Address

Problem

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.

Solution

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.

Phone Reset Problems

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.

Phone Resets Due to Intermittent Network Outages

Problem

Your network may be experiencing intermittent outages.

Solution

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.

Phone Resets Due to DHCP Setting Errors

Problem

The DHCP settings may be incorrect.

Solution

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.

Phone Resets Due to Incorrect Static IP Address

Problem

The static IP address assigned to the phone may be incorrect.

Solution

If the phone is assigned a static IP address, verify that you have entered the correct settings.

Phone Resets During Heavy Network Usage

Problem

If the phone appears to reset during heavy network usage, it is likely that you do not have a voice VLAN configured.

Solution

Isolating the phones on a separate auxiliary VLAN increases the quality of the voice traffic.

Phone Does Not Power Up

Problem

The phone does not appear to be powered up.

Solution

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.

Phone Cannot Connect to LAN

Problem

The physical connection to the LAN may be broken.

Solution

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.

Audio Problems

The following sections describe how to resolve audio problems.

No Speech Path

Problem

One or more people on a call do not hear any audio.

Solution

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.

Choppy Speech

Problem

A user complains of choppy speech on a call.

Cause

There may be a mismatch in the jitter configuration.

Solution

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.

General Telephone Call Problems

The following sections help troubleshoot general telephone call problems.

Phone Call Cannot Be Established

Problem

A user complains about not being able to make a call.

Cause

The phone does not have a DHCP IP address. The phones display the message Configuring IP or Registering.

Solution

  1. Verify the following:

    1. The Ethernet cable is attached.
    2. The Third-Party Call Control system is active.

  2. Enable audio server debug and capture logs on both phones, then examine the logs.

Phone Does Not Recognize DTMF Digits or Digits Are Delayed

Problem

The user complains that numbers are missed or delayed when the keypad is used.

Cause

Pressing the keys too quickly can result in missed or delayed digits.

Solution

Keys should not be pressed rapidly.

Report All Phone Issues with the Configuration Utlility

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.

Procedure
    Step 1   On the Phone Web page, select Admin Login > advanced > Info > Debug Info.
    Step 2   In the Problem Reports section, click Generate PRT. The Report Problem dialog appears.
    Step 3   Enter the following information in the Report Problem dialog:
    1. Enter the date that you experienced the problem in the Date field. The current date appears in this field by default.
    2. Enter the time that you experienced the problem in the Time field. The current time appears in this field by default.
    3. In the Select Problem drop-down list box, choose the description of the problem from the available options.
    Step 4   Click Submit in the Report Problem dialog.

    The Submit button is enabled only if you select a value in the Select Problem drop-down list box.

    You get a notification alert on the Phone Web page that indicates if the PRT upload was successful or not.

    Troubleshooting Procedures

    These procedures can be used to identify and correct problems.

    Check DHCP Settings

    Procedure
      Step 1   On the phone, press Applications .
      Step 2   Select Admin Settings > Network Setup > IPv4 Setup.
      Step 3   Check the DHCP server field.

      Check the DHCP option for enabled or disabled.

      Step 4   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 5   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

      Verify DNS Settings

      Procedure
        Step 1   On the phone, press Applications .
        Step 2   Select Admin Settings > Network Setup > IPv4 Setup
        Step 3   Check that the DNS Server 1 field is set correctly.
        Step 4   You should also verify that a CNAME entry was made in the DNS server for the TFTP server and for the Third-Party Call Control.

        You must also ensure that DNS is configured to do reverse lookups.

        Additional Troubleshooting Information

        If you have additional questions about troubleshooting your phone, go to the following Cisco website and navigate to the desired phone model:

        https:/​/​www.cisco.com/​cisco/​web/​psa/​troubleshoot.html