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Cisco Wireless IP Phone 7920 Administration Guide for Cisco CallManager Release 3.3 or Later
OL-3930-02
Chapter 9 Troubleshooting the Cisco Wireless IP Phone 7920
Resolving Voice Quality and Roaming Problems
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 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 the
“Modifying DHCP Settings” section on page 5-7 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 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 “Configuring Static Settings” section on page 5-9.
Verifying Voice VLAN Configuration
If the Cisco IP Phone appears to reset during heavy network usage (for example,
following extensive web surfing on a computer connected to same AP and switch
as phone), it is likely that you do not have a voice VLAN or the appropriate QoS
settings configured.