Default Cisco Ip Phone Support Configuration; Cisco Ip Phone Support Configuration Guidelines And Restrictions - Cisco 7609 Configuration Manual
Cisco ios software configuration guide—12.1e
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Default Cisco IP Phone Support Configuration
When a switching module port detects an unpowered Cisco IP Phone, the switching module reports to
the supervisor engine that an unpowered Cisco IP Phone is present and on which module and port. If the
port is configured in auto mode, the supervisor engine determines if there is enough system power
available to power up the Cisco IP Phone. If there is sufficient power available, the supervisor engine
removes the default-allocated power required by a Cisco IP Phone from the total available system power
and sends a message to the switching module instructing it to provide power to the port. If there is not
enough available power for the Cisco IP Phone, the supervisor engine sends a message to the switching
module indicating that power is denied to the port.
Cisco IP Phones may have different power requirements. The supervisor engine initially allocates the
configured default of 7 W (167 mA at 42V) to the Cisco IP Phone. When the correct amount of power
is determined from the CDPv2 messaging with the Cisco IP Phone, the supervisor engine reduces or
increases the allocated power.
For example, the default allocated power is 7 W. A Cisco IP Phone requiring 6.3W is plugged into a port.
The supervisor engine allocates 7 W for the Cisco IP Phone and powers it up. Once the Cisco IP Phone
is operational, it sends a CDPv2 message with the actual power requirement to the supervisor engine.
The supervisor engine then decreases the allocated power to the required amount.
When you power off the Cisco IP Phone through the CLI or SNMP or remove it, the supervisor engine
sends a message to the switching module to turn off the power on the port. That power is then returned
to the available system power.
Caution
When a Cisco IP Phone cable is plugged into a port and the power is turned on, the supervisor engine
has a 4-second timeout waiting for the link to go up on the line. During those 4 seconds, if the
Cisco IP Phone cable is unplugged and a network device is plugged in, the network device could be
damaged. We recommend that you wait at least 10 seconds between unplugging a network device and
plugging in another network device.
Default Cisco IP Phone Support Configuration
Cisco IP Phone support is disabled by default.
When the voice VLAN feature is enabled, all untagged traffic is sent with the default CoS priority of the
port.
The CoS is not trusted for 802.1P or 802.1Q tagged traffic.
Cisco IP Phone Support Configuration Guidelines and
Restrictions
When configuring IP phone supports, follow these guidelines and restrictions:
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•
•
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
11-4
You must enable the Cisco Discovery Protocol version 2 (CDPv2) on the Cisco 7600 series router
port connected to the Cisco IP Phone to send configuration information to the Cisco IP Phone.
You can configure a voice VLAN only on a Layer 2 LAN port.
You can configure the ports on WS-X6548-RJ-45 and WS-X6548-RJ-21 switching modules to trust
received Layer 2 CoS values (QoS port architecture 1p1q0t/1p3q1t). The WS-X6548-RJ-45 and
WS-X6548-RJ-21 switching modules cannot supply power to Cisco IP Phones.
Chapter 11
Configuring Cisco IP Phone Support
78-14064-04
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Troubleshooting
