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.
Phone Reset Problems
If users report that their phones are resetting during calls or while the phones are idle, you should investigate
the cause. If the network connection and Cisco Unified Communications Manager connection are stable, a
phone should not reset.
Typically, a phone resets if it has problems in connecting to the network or to Cisco Unified Communications
Manager.
Phone Cannot Connect to LAN
Problem
The physical connection to the LAN may be broken.
Solution
Verify that the Ethernet connection to which the Cisco IP Phone connects is up. For example, check whether
the particular port or switch to which the phone connects is down and that the switch is not rebooting. Also
ensure that no cable breaks exist.
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.
Cisco Unified IP Phone 8941 and 8945 Administration Guide for Cisco Unified Communications Manager 10.0 (SCCP
and SIP)
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Phone Reset Problems
