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Cisco Unified IP Phone 6921, 6941, 6945, and 6961 Administration Guide for Cisco Unified Communications Manager 8.5 (SCCP and SIP)
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Chapter
Cisco Unified IP Phone Resets Unexpectedly
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 Communications Manager
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
Communications Manager. These sections can help you identify the cause of a phone resetting in your
network:
• Verifying the Physical Connection, page 9-6
• Identifying Intermittent Network Outages, page 9-6
• Verifying DHCP Settings, page 9-6
• Checking Static IP Address Settings, page 9-7
• Verifying the Voice VLAN Configuration, page 9-7
• Verifying that the Phones Have Not Been Intentionally Reset, page 9-7
• Eliminating DNS or Other Connectivity Errors, page 9-7

Verifying the Physical Connection

Verify that the Ethernet connection to which the Cisco Unified IP Phone is connected is up. For example,
check whether the particular port or switch to which the phone is connected is down and that the switch
is not rebooting. Also make sure that there are no cable breaks.

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 Setup Menu”
section on page 4-4 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.