Cisco 7821 Administration Guide

Phone Resets Due to Incorrect Static IP Address
Problem
The static IP address assigned to the phone may be incorrect.
Solution
If the phone is assigned a static IP address, verify that you have entered the correct settings.
Phone Resets During Heavy Network Usage
Problem
If the phone appears to reset during heavy network usage, it is likely that you do not have a voice VLAN
configured.
Solution
Isolating the phones on a separate auxiliary VLAN increases the quality of the voice traffic.
Phone Does Not Power Up
Problem
The phone does not appear to be powered up.
Solution
In most cases, a phone restarts if it powers up by using external power but loses that connection and switches
to PoE. Similarly, a phone may restart if it powers up by using PoE and then connects to an external power
supply.
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.
Cisco IP Phone 7800 Series Multiplatform Phones Administration Guide
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Cisco IP Phone Troubleshooting
Phone Resets Due to Incorrect Static IP Address

Cisco 7821 Specifications

General

Brand	Cisco
Model	7821
Category	IP Phone
Language	English