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Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified Communications Manager 7.0 (SCCP)
OL-15498-01
Chapter 8 Troubleshooting and Maintenance
Cisco Unified IP Phone Resets Unexpectedly
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 4-4 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.
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 4-4 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 on page 2-3 for
details.