Cisco 7912G - Manual (Page 113)

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Cisco Unified IP Phone Administration Guide for Cisco Unified CallManager 5.0 (SIP), Cisco Unified IP Phones
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Chapter 7 Troubleshooting the Cisco Unified IP Phone
Cisco Unified IP Phone Resets Unexpectedly
Verifying DHCP Settings
The following procedure 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
Table 4-2 on page 4-19 for details.
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
Table 4-2 on page 4-19 .
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 Cisco Catalyst Family of Switches” section on page 2-3 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.