Cisco 8961 Administration Manual page 295

Troubleshooting and Maintenance
Cisco Unified 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.
Cisco Unified IP Phone Resets Unexpectedly
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 Cisco Unified Communications Manager connection are
stable, a Cisco Unified IP Phone should not reset.
Typically, a phone resets if it has problems in connecting to the Ethernet network or to Cisco Unified
Communications Manager. These sections can help you identify the cause of a phone resets in your network:
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.
DHCP Setting Errors
Problem
The DHCP settings may be incorrect.
Solution
Verify that you have properly configured the phone to use DHCP. See
more information. Verify that the DHCP server is set up properly. Verify the DHCP lease duration. Cisco
recommends that you set it to 8 days.
REVIEW DRAFT - CISCO CONFIDENTIAL
Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 10.0
Cisco Unified IP Phone Resets Unexpectedly
Ethernet Setup menu, on page 104
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