Identifying Intermittent Network Outages; Verifying Dhcp Settings; Checking Static Ip Address Settings; Verifying Voice Vlan Configuration - Cisco 7940G Administration Manual

Chapter 7 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.

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

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 VLAN" section on page 2-2
details.

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 models 7960G/7940G 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:
Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified Communications Manager 7.0 (SIP)
OL-15499-01
Verify that you have properly configured the phone to use DHCP. See the
Menu" section on page 4-4
Verify that the DHCP server has been set up properly.
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.
"Network Configuration Menu" section on page 4-4
for more information.
for more information.
Cisco Unified IP Phone Resets Unexpectedly
"Network Configuration
for
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