Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified CallManager 5.0 (SIP)
Troubleshooting and Maintenance
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Troubleshooting and Maintenance

Table Of Contents

Troubleshooting and Maintenance

Resolving Startup Problems

Symptom: The Cisco Unified IP Phone Does Not Go Through its Normal Startup Process

Symptom: The Cisco Unified IP Phone Does Not Register with Cisco Unified CallManager

Identifying Error Messages

Registering the Phone with Cisco Unified CallManager

Checking Network Connectivity

Verifying TFTP Server Settings

Verifying IP Addressing and Routing

Verifying DNS Settings

Verifying Cisco Unified CallManager Settings

Cisco Unified CallManager and TFTP Services Are Not Running

Creating a New Configuration File

Symptom: Cisco Unified IP Phone Unable to Obtain IP Address

Cisco Unified IP Phone Resets Unexpectedly

Verifying Physical Connection

Identifying Intermittent Network Outages

Verifying DHCP Settings

Checking Static IP Address Settings

Verifying Voice VLAN Configuration

Verifying that the Phones Have Not Been Intentionally Reset

Eliminating DNS or Other Connectivity Errors

Troubleshooting Cisco Unified IP Phone Security

General Troubleshooting Tips for the Cisco Unified IP Phone

Resetting or Restoring the Cisco Unified IP Phone

Performing a Basic Reset

Performing a Factory Reset

Where to Go for More Troubleshooting Information

Cleaning the Cisco Unified IP Phone


Troubleshooting and Maintenance


This chapter provides information that can assist you in troubleshooting problems with your Cisco Unified IP Phone or in your IP telephony network.

For additional troubleshooting information, refer to the Using the 79xx Status Information For Troubleshooting tech note. This document is available to registered Cisco.com users at this URL:

http://www.cisco.com/warp/customer/788/AVVID/telecaster_trouble.html

If you need additional troubleshooting assistance, you can contact the Cisco TAC. The phone generates detailed logs that can assist the Cisco TAC with troubleshooting and resolving problems.

This chapter includes these topics:

Resolving Startup Problems

Cisco Unified IP Phone Resets Unexpectedly

Troubleshooting Cisco Unified IP Phone Security

General Troubleshooting Tips for the Cisco Unified IP Phone

Resetting or Restoring the Cisco Unified IP Phone

Where to Go for More Troubleshooting Information

Cleaning the Cisco Unified IP Phone

Resolving Startup Problems

After installing a Cisco Unified IP Phone into your network and adding it to Cisco Unified CallManager, the phone should start up as described in the "Verifying the Phone Startup Process" section. If the phone does not start up properly, see the following sections for troubleshooting information:

Symptom: The Cisco Unified IP Phone Does Not Go Through its Normal Startup Process

Symptom: The Cisco Unified IP Phone Does Not Register with Cisco Unified CallManager

Symptom: Cisco Unified IP Phone Unable to Obtain IP Address

Symptom: The Cisco Unified IP Phone Does Not Go Through its Normal Startup Process

When you connect a Cisco Unified IP Phone into the network port, the phone should go through its normal startup process and the LCD screen should 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, and so on. Or, the phone may not be functional.

To determine whether the phone is functional, follow these suggestions to systematically eliminate these other potential problems:

1. Verify that the network port is functional:

Exchange the Ethernet cables with cables that you know are functional.

Disconnect a functioning Cisco Unified IP Phone from another port and connect it to this network port to verify the port is active.

Connect the Cisco Unified IP Phone that will not start up to a different port that is known to be good.

Connect the Cisco Unified IP Phone that will not start up directly to the port on the switch, eliminating the patch panel connection in the office.

2. Verify that the phone is receiving 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 after attempting these solutions, the LCD screen on the Cisco Unified IP Phone does not display any characters after at least five minutes, perform a factory reset of the phone (see the "Performing a Factory Reset" section). If the phone still does not display characters, contact a Cisco technical support representative for additional assistance.

Symptom: The Cisco Unified IP Phone Does Not Register with Cisco Unified CallManager

If the phone proceeds past the first stage of the startup process (LED buttons flashing on and off) but continues to cycle through the messages displaying on the LCD screen, the phone is not starting up properly. The phone cannot successfully start up unless it is connected to the Ethernet network and it has registered with a Cisco Unified CallManager server.

These sections can assist you in determining the reason the phone is unable to start up properly:

Identifying Error Messages

Registering the Phone with Cisco Unified CallManager

Checking Network Connectivity

Verifying TFTP Server Settings

Verifying IP Addressing and Routing

Verifying DNS Settings

Verifying Cisco Unified CallManager Settings

Cisco Unified CallManager and TFTP Services Are Not Running

Creating a New Configuration File

In addition, problems with security may prevent the phone from starting up properly. See the "Troubleshooting Cisco Unified IP Phone Security" section for more information.

Identifying Error Messages

As the Cisco Unified IP Phone models 7960G/7940G cycle through the startup process, you can access status messages that might provide you with information about the cause of a problem. See the "Status Messages Screen" section on page 6-1 for instructions about accessing status messages and for a list of potential errors, their explanations, and their solutions.

Registering the Phone with Cisco Unified CallManager

A Cisco Unified IP Phone can register with a Cisco Unified CallManager server only if the phone has been added to the server or if auto-registration is enabled. Review the information and procedures in the "Adding Phones to the Cisco Unified CallManager Database" section to ensure that the phone has been added to the Cisco Unified CallManager database.

To verify that the phone is in the Cisco Unified CallManager database, choose Device > Phone > Find from Cisco Unified CallManager Administration to search for the phone based on its MAC Address. For information about determining a MAC address, see the "Determining the MAC Address for a Cisco Unified IP Phone" section.

If the phone is already in the Cisco Unified CallManager database, its configuration file may be damaged. See the "Creating a New Configuration File" section for assistance.

Checking Network Connectivity

If the network is down between the phone and the TFTP server or Cisco Unified CallManager, the phone cannot start up properly. Ensure that the network is currently running.

Verifying TFTP Server Settings

The Cisco Unified IP Phone uses the TFTP Server 1 setting to identify the primary TFTP server used by the phone. You can determine this setting by pressing the Settings button on the phone, choosing Network Configuration, and scrolling to the TFTP Server 1 option.

If you have assigned a static IP address to the phone, you must manually enter a setting for the TFTP Server 1 option. See the "Network Configuration Menu" section on page 4-6.

If you are using DHCP, the phone obtains the address for the TFTP server from the DHCP server. Check the IP address configured in Option 150.

You can also enable the phone to use an alternate TFTP server. Such a setting is particularly useful if the phone was recently moved from a from one location to another. See the "Network Configuration Menu" section on page 4-6 for instructions.

Verifying IP Addressing and Routing

You should verify the IP addressing and routing settings on the phone. If you are using DHCP, the DHCP server should provide these values. If you have assigned a static IP address to the phone, you must enter these values manually.

On the Cisco Unified IP Phone, press the Settings button, choose Network Configuration, and look at the following options:

DHCP Server—If you have assigned a static IP address to the phone, you do not need to enter a value for the DHCP Server option. However, if you are using a DHCP server, this option must have a value. If it does not, check your IP routing and VLAN configuration. Refer to Troubleshooting Switch Port Problems, available at this URL: http://www.cisco.com/warp/customer/473/53.shtml

IP Address, Subnet Mask, Default Router—If you have assigned a static IP address to the phone, you must manually enter settings for these options. See the "Network Configuration Menu" section on page 4-6 for instructions.

If you are using DHCP, check the IP addresses distributed by your DHCP server. Refer to Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks, available at this URL: http://www.cisco.com/warp/customer/473/100.html#41

Verifying DNS Settings

If you are using DNS to refer to the TFTP server or to Cisco Unified CallManager, you must ensure that you have specified a DNS server. You should also verify that there is a CNAME entry in the DNS server for the TFTP server and for the Cisco Unified CallManager system.

Verifying Cisco Unified CallManager Settings

On the Cisco Unified IP Phone, press the Settings button, choose Network Configuration, and look at the CallManager 1-5 options. The Cisco Unified IP Phone attempts to open a TCP connection to all the Cisco Unified CallManager servers that are part of the assigned Cisco Unified CallManager group. If none of these options contain IP addresses or show Active or Standby, the phone is not properly registered with Cisco Unified CallManager. See the "Registering the Phone with Cisco Unified CallManager" section for tips on resolving this problem.

Cisco Unified CallManager and TFTP Services Are Not Running

If the Cisco Unified CallManager or TFTP services are not running, phones may not be able to start up properly. However, in such a situation, it is likely that you are experiencing a system-wide failure and that other phones and devices are unable to start up properly.

If the Cisco Unified CallManager service is not running, all devices on the network that rely on it to make phone calls will be affected. If the TFTP service is not running, many devices will not be able to start up successfully.

To start a service, follow these steps:

Procedure


Step 1 From Cisco Unified CallManager Administration, choose Serviceability from the Navigation drop-down list.

Step 2 Choose Tools > Control Center - Network Services.

Step 3 Choose the primary Cisco Unified CallManager server from the Server drop-down list.

The page displays the service names for the server that you chose, the status of the services, and a service control panel to stop or start a service.

Step 4 If a service has stopped, click its radio button and then click the Start button.

The Service Status symbol changes from a square to an arrow.


Creating a New Configuration File

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.

To create a new configuration file, follow these steps:

Procedure


Step 1 From Cisco Unified CallManager, choose Device > Phone > Find to locate the phone experiencing problems.

Step 2 Choose Delete to remove the phone from the Cisco Unified CallManager database.

Step 3 Add the phone back to the Cisco Unified CallManager database. See the "Adding Phones to the Cisco Unified CallManager Database" section for details.

Step 4 Power cycle the phone:

If the phone receives power from an external power source, unplug the Ethernet cable from the Network port on the phone, then unplug the power supply from the DC adaptor port on the phone. Next, reconnect the power supply and then reconnect the Ethernet cables.


Caution Always unplug the upstream Ethernet cable from the phone before unplugging the power supply. Unplugging the power supply before unplugging the upstream Ethernet cable could result in a service interruption on the network.

If the phone receives inline power, unplug the cable from the Network port on the phone and then plug it back in.



NoteWhen you remove a phone from the Cisco Unified CallManager database, its configuration file is deleted from the Cisco Unified CallManager TFTP server. The phone's directory number or numbers remain in the Cisco Unified CallManager database. They are called "unassigned DNs" and can be used for other devices. If unassigned DNs are not used by other devices, delete them from the Cisco Unified CallManager database. You can use the Route Plan Report to view and delete unassigned reference numbers. Refer to Cisco Unified CallManager Administration Guide for more information.

Changing the buttons on a phone button template, or assigning a different phone button template to a phone, may result in directory numbers that are no longer accessible from the phone. The directory numbers are still assigned to the phone in the Cisco Unified CallManager database, but there is no button on the phone with which calls can be answered. These directory numbers should be removed from the phone and deleted if necessary.


Symptom: Cisco Unified IP Phone Unable to Obtain IP Address

If a phone is unable to obtain an IP address when it starts up, the phone may be not be on the same network or VLAN as the DHCP server, or the switch port to which the phone is connected may be disabled.

Make sure that the network or VLAN to which the phone is connected has access to the DHCP server, and make sure that the switch port is enabled.

Cisco Unified IP Phone Resets Unexpectedly

If users report that their phones are resetting during calls or while idle on their desk, you should investigate the cause. If the network connection and Cisco Unified CallManager connection are stable, a Cisco Unified IP Phone should not reset on its own.

Typically, a phone resets if it has problems connecting to the Ethernet network or to Cisco Unified CallManager. These sections can help you identify the cause of a phone resetting in your network:

Verifying Physical Connection

Identifying Intermittent Network Outages

Verifying DHCP Settings

Checking Static IP Address Settings

Verifying Voice VLAN Configuration

Verifying that the Phones Have Not Been Intentionally Reset

Eliminating DNS or Other Connectivity Errors

Verifying Physical Connection

Verify that the Ethernet connection to which the Cisco Unified IP Phone is connected is up. For example, check if the particular port or switch to which the phone is connected is down.

Identifying Intermittent Network Outages

Intermittent network outages affect data and voice traffic differently. Your network might have been 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 its network connection.

If you are experiencing problems with the voice network, you should investigate whether an existing problem is simply being exposed.

Verifying DHCP Settings

The following suggestions can help you determine if the phone has been properly configured to use DHCP:

1. Verify that you have properly configured the phone to use DHCP. See the "Network Configuration Menu" section on page 4-6 for more information.

2. Verify that the DHCP server has been set up properly.

3. Verify the DHCP lease duration. Cisco recommends that you set it to 8 days.

Cisco Unified IP Phones send messages with request type 151 to renew their DHCP address leases. If the DHCP server expects messages with request type 150, the lease will be denied, forcing the phone to restart and request a new IP address from the DHCP server.

Checking Static IP Address Settings

If the phone has been assigned a static IP address, verify that you have entered the correct settings. See the "Network Configuration Menu" section on page 4-6 for more information.

Verifying Voice VLAN Configuration

If the Cisco Unified IP Phone appears to reset during heavy network usage (for example, following extensive web surfing on a computer connected to same switch as phone), 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. See the "Understanding How the Cisco Unified IP Phone Interacts with the VLAN" section for details.

Verifying that the Phones Have Not Been Intentionally Reset

If you are not the only administrator with access to Cisco Unified CallManager, you should verify that no one else has intentionally reset the phones.

You can check whether a Cisco Unified IP Phone models 7960G/7940G received a command from Cisco Unified CallManager to reset by pressing the Settings button on the phone and choosing Status > Network Statistics. If the phone was recently reset one of these messages appears:

Reset-Reset—Phone closed due to receiving a Reset/Reset from Cisco Unified CallManager administration.

Reset-Restart—Phone closed due to receiving a Reset/Restart from Cisco Unified CallManager administration.

Eliminating DNS or Other Connectivity Errors

If the phone continues to reset, follow these steps to eliminate DNS or other connectivity errors:

Procedure


Step 1 Reset the phone to factory defaults. See the "Resolving Startup Problems" section for details.

Step 2 Modify DHCP and IP settings:

a. Disable DHCP. See the "Network Configuration Menu" section on page 4-6 for instructions.

b. Assign static IP values to the phone. See the "Network Configuration Menu" section on page 4-6 for instructions. Use the same default router setting used for other functioning Cisco Unified IP Phones.

c. Assign a TFTP server. See the "Network Configuration Menu" section on page 4-6 for instructions. Use the same TFTP server used for other functioning Cisco Unified IP Phones.

Step 3 On the Cisco Unified CallManager server, verify that the local host files have the correct Cisco Unified CallManager server name mapped to the correct IP address.

Step 4 From Cisco Unified CallManager, 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 CallManager, 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.

Step 6 Power cycle the phone:

If the phone receives power from an external power source, unplug the Ethernet cable from the Network port on the phone, then unplug the power supply from the DC adaptor port on the phone. Next, reconnect the power supply and then reconnect the Ethernet cable.


Caution Always unplug the upstream Ethernet cable from the phone before unplugging the power supply. Unplugging the power supply before unplugging the upstream Ethernet cable could result in a service interruption on the network.

If the phone receives inline power, unplug the cable from the Network port on the phone and then plug it back in.

Troubleshooting Cisco Unified IP Phone Security

Table 7-1 provides troubleshooting information for the security features on the Cisco Unified IP Phone. For information relating to the solutions for any of these issues, and for additional troubleshooting information about security and encryption, refer to Cisco Unified CallManager Security Guide.

Because third-party troubleshooting tools that sniff media and TCP packets do not work after you enable encryption, you must use Cisco Unified CallManager Administration to perform the following tasks if a problem occurs:

Analyze TCP packets for SCCP messages that are exchanged between Cisco Unified CallManager and the device

Extract the media encryption key material from SCCP messages and decrypt the media between the devices

Table 7-1 Cisco Unified IP Phone Security Troubleshooting 

Problem
Possible Cause

Phone reports TFTP authorization failure.

The TFTP address for the phone does not exist in the CTL file.

If you created a new CTL file with a new TFTP record, the existing CTL file on the phone may not contain a record for the new TFTP server.

Phone does not request signed configuration files.

The CTL file does not contain any TFTP server entry.

The CTL file does not contain any TFTP entries with certificates


General Troubleshooting Tips for the Cisco Unified IP Phone

Table 7-2 provides general troubleshooting information for the Cisco Unified IP Phone.

Table 7-2 Cisco Unified IP Phone Troubleshooting 

Summary
Explanation

Daisy-chaining IP phones.

Do not connect an IP phone to another IP phone through the access port. Each IP phone should directly connect to a switch port. If you connect IP phones together in a line (daisy-chaining), a problem with one phone can affect all subsequent phones in the line. Also, all phones on the line share bandwidth.

Poor quality when calling digital cell phones using the G.729 protocol.

In Cisco Unified CallManager, 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 re-register.

Prolonged broadcast storms (lasting several minutes) on the voice VLAN cause the IP phones to re-register with another Cisco Unified CallManager server.

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.


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.

Changing the telephone configuration.

By default, the network configuration options are locked to prevent users from making changes that could impact their network connectivity. You must unlock the network configuration options before you can configure them. See the "Unlocking and Locking Options" section on page 4-3 for details.

Phone resetting.

The phone resets when it loses contact with the Cisco Unified CallManager software. This lost connection can be due to any network connectivity disruption, including cable breaks, switch outages, and switch reboots.

LCD display issues.

If the display appears to have rolling lines or a wavy pattern, it might be interacting with certain types of older fluorescent lights in the building. Moving the phone away from the lights, or replacing the lights, should resolve the problem.

Dual-Tone Multi-Frequency (DTMF) delay.

When you are on a call that requires keypad input, if you press the keys too quickly, some of them might not be recognized.

Codec mismatch between the phone and another device.

The RxType and the TxType that is being used for a conversation between this IP phone and the other device 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.

Sound sample mismatch between the phone and another device.

The size of the voice packets that are being used in a conversation between this IP phone and the other device should match.

Gaps in voice calls.

Can be caused by a problem with jitter on the network or periodic high rates of network activity.

Checking signaling.

To check that signaling is working properly between the phone and Cisco Unified CallManager, press the Speaker button on the phone to answer a call. If you can answer a call and if you hear a dial tone, signaling is working properly.

Checking the handset cradle clip.

Cisco Unified IP Phones are designed with a reversible handset clip in the cradle. This clip is used with the plastic tab protruding out when the phone is in a vertical (wall-mounted) position. The position of the tab can interfere with the handset as it is placed in the cradle. If the phone remains in the on-hook position you may experience continued ringing when you try to answer a call or a lack of dial tone when you try to place a call. To resolve this problem, you may need to reverse the clip.

If the handset cradle clip is in the wall-mounted position and your phone is placed on a desktop, slide the clip upward to remove it. Rotate the clip 180 degrees and slide it back in so that the tab is hidden.

If the hook switch remains in the down position, tapping on the phone should free up the switch. You can also try pushing and suddenly releasing the off-hook button after the handset has been picked up.

Checking the hook switch contacts.

The hook switch contacts on the phone use a wiping action to self-clean the contacts. If your phone is not used regularly, dust and other airborne contaminants may degrade the contact performance and cause problems with operation. If you have periods of limited phone usage, you can clean the contacts by quickly pressing and releasing the hook switch a dozen times.

Checking the position of the phone.

The footstand of the phone allows adjustment of the phone to eliminate glare on the LCD screen. When the phone is in the most vertical position, the phone may be forced forward and the handset may not sit properly in the cradle, creating a false off-hook condition. Cisco recommends that you position the phone one notch from the most vertical position to ensure that the handset is firmly resting on the hook switch.

Checking the LAN cable.

Make sure that the LAN cable connected to the phone is positioned properly. The LAN cable should pass out of the side of the phone between the base and the footstand. If you are using a cable (such as Cat-5E or Cat-6) with a larger diameter than the cable that was packaged with your phone, the cable may cause the phone to tilt forward and force it off-hook. Use a smaller LAN cable to eliminate this problem.

Loopback condition.

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

The SW Port Configuration option in the Network Configuration menu on the phone is set to 10H
(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 will appear in the switch console log:

HALF_DUX_COLLISION_EXCEED_THRESHOLD

To resolve this problem, re-enable the port from the switch.


Resetting or Restoring the Cisco Unified IP Phone

There are two general methods for resetting or restoring the Cisco Unified IP Phone:

Performing a Basic Reset

Performing a Factory Reset

Performing a Basic Reset

Performing a basic reset of a Cisco Unified IP Phone provides a way to recover if the phone experiences an error and provides a way to reset or restore various configuration and security settings.

A basic reset resets any user and network configuration changes that you have made but that the phone has not written to its Flash memory to previously-saved settings, then restarts the phone.

To perform a basic reset, hold down the * and the 6 keys, and press the Settings button.

Performing a Factory Reset

When you perform a factory reset of the Cisco Unified IP Phone, the following information is erased or reset to its default value:

CTL file—Erased

User configuration settings—Reset to default values

Network configuration settings—Reset to default values (optional)

Locale information—Reset to default value

Call histories—Erased

To perform a factory reset of a phone, perform the following steps.


Note The phone must be on a DHCP-enabled network before you can perform these steps.


Procedure


Step 1 Unplug the power cable from the phone and then plug it back in.

The phone begins its power up cycle.

Step 2 Immediately press and hold # while the Headset, Mute, and Speaker buttons turn on and off in sequence.

Release # after the Speaker button turns off.

The Headset, Mute, and Speaker buttons flash in sequence to indicate that the phone is waiting for you to enter the key sequence for the reset.

Step 3 Press 123456789*0# within 60 seconds after the Headset, Mute, and Speaker buttons begin to flash.

If you repeat a key within the sequence (for example, if you press 1223456789*0#), the sequence will still be accepted and the phone will reset.

If you do not complete this key sequence or do not press any keys, the Headset, Mute, and Speaker buttons will stop flashing after 60 seconds and the phone will continue with its normal startup process. The phone will not reset.

If you enter an invalid key sequence, the buttons will stop flashing immediately and the phone will continue with its normal startup process. The phone will not reset.

If you enter this key sequence correctly, the phone displays this prompt:

Keep network cfg? 1 = yes 2 = no

Step 4 To maintain existing network configuration settings for the phone when the phone resets, press 1. To reset network configuration settings when the phone resets, press 2.

If you press another key or do not respond to this prompt within 60 seconds, the will continue with its normal startup process and will not reset.

Otherwise, the phone goes through the factory reset process.


Where to Go for More Troubleshooting Information

If you have additional questions about troubleshooting the Cisco Unified IP Phones, several Cisco.com web sites can provide you with more tips. Choose from the sites available for your access level.

Cisco Unified IP Phone Troubleshooting Resources:

http://www.cisco.com/en/US/products/hw/phones/ps379/tsd_products_
support_series_home.html

Cisco Unified Products and Services (Technical Support and Documentation):

http://www.cisco.com/en/US/products/sw/voicesw/tsd_products_support_
category_home.html

Cleaning the Cisco Unified IP Phone

To clean your Cisco Unified IP phone, use only a dry soft cloth to gently wipe the phone and the LCD screen. Do not apply liquids or powders directly on the phone. As with all non-weather-proof electronics, liquids and powders can damage the components and cause failures.