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Chapter 9
Troubleshooting and Maintenance
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.
2.
3.
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 renewal is 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
Network Configuration Menu, page 4-5
Verifying the 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 the same switch as the 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
Understanding How the Cisco Unified IP Phones Interact with the VLAN, page 2-2
Verifying that the Phones Have Not Been Intentionally Reset
If you are not the only administrator with access to Cisco Unified Communications Manager, you should
verify that no one else has intentionally reset the phones.
You can check whether a Cisco Unified IP Phone received a command from Cisco Unified
Communications Manager to reset by pressing the Settings button on the phone and choosing Status >
Network Statistics. If the phone was recently reset one of these messages appears:
•
OL-23091-01
Verify that you have properly configured the phone to use DHCP. See
page 4-5
for more information.
Verify that the DHCP server has been set up properly.
Verify the DHCP lease duration. We recommend that you set the lease duration to 8 days.
Reset-Reset—Phone received a Reset/Reset request from Cisco Unified Communications Manager
Administration.
Cisco Unified IP Phone Administration Guide for Cisco Unified Communications Manager 8.6 (SCCP and SIP)
Cisco Unified IP Phone Resets Unexpectedly
for more information.
Network Configuration Menu,
for details.
9-7
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Table of Contents
Troubleshooting
