Cisco 7800 Series Administration Manual page 187

Cisco 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 IP Phone Reset Problems
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 Third Party Call Control connection are stable, a Cisco
IP Phone should not reset.
Typically, a phone resets if it has problems in connecting to the Ethernet network or to Third Party Call
Control.
Phone Resets Due to 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.
Phone Resets Due to DHCP Setting Errors
Problem
The DHCP settings may be incorrect.
Solution
Verify that you have properly configured the phone to use DHCP. Verify that the DHCP server is set up
properly. Verify the DHCP lease duration. We recommend that you set the lease duration to 8 days.
Cisco IP Phone 7800 Series for Third-Party Call Control Administration Guide
Cisco IP Phone Reset Problems
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