General Troubleshooting Tips - Cisco 7970G - IP Phone VoIP Administration Manual

Chapter 9 Troubleshooting and Maintenance

General Troubleshooting Tips

Cisco Unified IP Phone 7970G/7971G-GE Administration Guide for Cisco Unified Communications Manager 6.1
OL-14626-01
Table 9-2 provides general troubleshooting information for the Cisco Unified IP
Phone.
Table 9-2 Cisco Unified IP Phone Troubleshooting
Summary
Daisy-chaining IP
phones
Poor quality when
calling digital cell
phones using the G.729
protocol
Prolonged broadcast
storms cause IP phones
to reset, or be unable to
make or answer a call
Explanation
Cisco does not support connecting an IP phone to
another IP phone through the PC port. Each IP phone
should directly connect to a switch port. If phones
are connected together in a line (by using the PC
port), the phones will not work.
In Cisco Unified Communications Manager, you can
configure the network to use the G.729 protocol (the
default is G.711). When using G.729, calls between
an IP phone and a digital cellular phone will have
poor voice quality. Use G.729 only when absolutely
necessary.
A prolonged Layer 2 broadcast storm (lasting several
minutes) on the voice VLAN may cause IP phones to
reset, lose an active call, or be unable to initiate or
answer a call. Phones may not come up until a
broadcast storm ends.
General Troubleshooting Tips
9-15