Cisco 7600 Series Router Software Configuration Guide, Cisco IOS Release 15S
Configuring Cisco IP Phone Support
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Table of Contents

Configuring CiscoIPPhone Support

Understanding CiscoIPPhone Support

CiscoIPPhone Connections

CiscoIPPhone Voice Traffic

CiscoIPPhone Data Traffic

CiscoIPPhone Power Configurations

Locally Powered CiscoIPPhones

Inline-Powered CiscoIPPhones

Default CiscoIPPhone Support Configuration

CiscoIPPhone Support Configuration Guidelines and Restrictions

Configuring CiscoIPPhone Support

Configuring Voice Traffic Support

Configuring Data Traffic Support

Configuring Inline Power Support

Configuring Cisco IP Phone Support

This chapter describes how to configure support for Cisco IP phones on the Cisco 7600 series routers .


Note For complete syntax and usage information for the commands used in this chapter, refer to the Cisco 7600 Series Routers Command References at this URL:

http://www.cisco.com/en/US/products/hw/routers/ps368/prod_command_reference_list.html


 

This chapter consists of these sections:

Understanding Cisco IP Phone Support

These sections describe Cisco IP phone support:

Cisco IP Phone Connections

The Cisco IP phone contains an integrated 3-port 10/100 switch. The ports are dedicated connections to these devices:

  • Port 1 connects to the router.
  • Port 2 is an internal 10/100 interface that carries the Cisco IP phone traffic.
  • Port 3 connects to a PC or other device.

Figure 16-1 shows a Cisco IP phone connected between a router and a PC.

Figure 16-1 Cisco IP Phone Connected to a Switch

 

Cisco IP Phone Voice Traffic

The Cisco IP phone transmits voice traffic with Layer 3 IP precedence and Layer 2 CoS values, which are both set to 5 by default. The sound quality of a Cisco IP phone call can deteriorate if the voice traffic is transmitted unevenly. To provide more predictable voice traffic flow, you can configure QoS to trust the Layer 3 IP precedence or Layer 2 CoS value in the voice traffic (refer to Chapter 48, “Configuring PFC QoS”).


Note 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. Configure QoS policies that use the Layer 3 IP precedence value on other switching modules.


You can configure a Layer 2 access port with an attached Cisco IP phone to use one VLAN for voice traffic and another VLAN for data traffic from a device attached to the Cisco IP phone.

You can configure Layer 2 access ports on the router to send Cisco Discovery Protocol (CDP) packets that instruct an attached Cisco IP phone to transmit voice traffic to the router in any of the following ways:

  • In the voice VLAN, tagged with a Layer 2 CoS priority value
  • In the access VLAN, tagged with a Layer 2 CoS priority value
  • In the access VLAN, untagged (no Layer 2 CoS priority value)

Note In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5 for voice traffic and 3 for voice control traffic).


You cannot use Cisco IOS software commands to configure the frame type used by data traffic sent from a device attached to the access port on the Cisco IP phone.

Cisco IP Phone Data Traffic


Note Untagged traffic from the device attached to the Cisco IP phone passes through the Cisco IP phone unchanged, regardless of the trust state of the access port on the Cisco IP phone.


To process tagged data traffic (traffic in 802.1Q or 802.1p frame types) from the device attached to the access port on the Cisco IP phone (see Figure 16-1), you can configure Layer 2 access ports on the router to send CDP packets that instruct an attached Cisco IP phone to configure the access port on the Cisco IP phone to either of these two modes:

  • Trusted mode—All traffic received through the access port on the Cisco IP phone passes through the Cisco IP phone unchanged.
  • Untrusted mode—All traffic in 802.1Q or 802.1p frames received through the access port on the Cisco IP phone is marked with a configured Layer 2 CoS value. The default Layer 2 CoS value is 0. Untrusted mode is the default.

Cisco IP Phone Power Configurations

These sections describe Cisco IP phone power configurations:

Locally Powered Cisco IP Phones

There are two varieties of local power:

  • From a power supply connected to the Cisco IP phone
  • From a power supply through a patch panel over the twisted-pair Ethernet cable to the Cisco IP phone

When a locally powered Cisco IP phone is present on a switching module port, the switching module cannot detect its presence. The supervisor engine discovers the Cisco IP phone through CDP messaging with the Cisco IP phone.

If a locally powered Cisco IP phone loses local power and the mode is set to auto , the switching module discovers the Cisco IP phone and informs the supervisor engine, which then supplies inline power to the Cisco IP phone.

Inline-Powered Cisco IP Phones

Inline power is from switching modules that support an inline power daughtercard. Inline power is sent over the twisted-pair Ethernet cable to the Cisco IP phone.


Note For information about switching modules that support inline power, refer to the Release Notes for Cisco IOS Release Release Notes for Cisco IOS Release 12.2SX on the Supervisor Engine 720, Supervisor Engine 32, and Supervisor Engine 2 publication.


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 42 V) to the Cisco IP phone. When the correct amount of power is determined from the CDP 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 6.3 W 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 CDP 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

The following guidelines and restrictions apply when configuring Cisco IP phone support:

  • You must enable the Cisco Discovery Protocol (CDP) 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.
  • You cannot configure 10/100 Mbps ports with QoS port architecture 1p4t/2q2t to trust received Layer 2 CoS values. Configure policies to trust the Layer 3 IP precedence value on switching modules with QoS port architecture 1p4t/2q2t.
  • The following conditions indicate that the Cisco IP phone and a device attached to the Cisco IP phone are in the same VLAN and must be in the same IP subnet:

If they both use 802.1p or untagged frames

If the Cisco IP phone uses 802.1p frames and the device uses untagged frames

If the Cisco IP phone uses untagged frames and the device uses 802.1p frames

If the Cisco IP phone uses 802.1Q frames and the voice VLAN is the same as the access VLAN

  • The Cisco IP phone and a device attached to the Cisco IP phone cannot communicate if they are in the same VLAN and subnet but use different frame types, because traffic between devices in the same subnet is not routed (routing would eliminate the frame type difference).
  • You cannot use Cisco IOS software commands to configure the frame type used by traffic sent from a device attached to the access port on the Cisco IP phone.
  • If you enable port security on a port configured with a voice VLAN and if there is a PC connected to the Cisco IP phone, set the maximum allowed secure addresses on the port to at least 3.
  • You cannot configure static secure MAC addresses in the voice VLAN.
  • Ports configured with a voice VLAN can be secure ports (see Chapter 54, “Configuring Port Security”).
  • In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5 for voice traffic and 3 for voice control traffic).

Configuring Cisco IP Phone Support

These sections describe how to configure Cisco IP phone support:

Configuring Voice Traffic Support

To configure the way in which the Cisco IP phone transmits voice traffic, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface fastethernet slot/port

Selects the port to configure.

Step 2

Router(config-if)# switchport voice vlan { voice_vlan_ID | dot1p | none | untagged }

Configures the way in which the Cisco IP phone transmits voice traffic.

Router(config-if)# no switchport voice vlan

Clears the configuration.

Step 3

Router(config)# end

Exits configuration mode.

Step 4

Router# show interfaces fastethernet slot/port switchport

Router# show running-config interface fastethernet slot/port

Verifies the configuration.

When configuring the way in which the Cisco IP phone transmits voice traffic, note the following information:

  • Enter a voice VLAN ID to send CDP packets that configure the Cisco IP phone to transmit voice traffic in 802.1Q frames, tagged with the voice VLAN ID and a Layer 2 CoS value (the default is 5). Valid VLAN IDs are from 1 to 4094. The router puts the 802.1Q voice traffic into the voice VLAN.
  • Enter the dot1p keyword to send CDP packets that configure the Cisco IP phone to transmit voice traffic in 802.1p frames, tagged with VLAN ID 0 and a Layer 2 CoS value (the default is 5 for voice traffic and 3 for voice control traffic). The router puts the 802.1p voice traffic into the access VLAN.
  • Enter the untagged keyword to send CDP packets that configure the Cisco IP phone to transmit untagged voice traffic. The router puts the untagged voice traffic into the access VLAN.
  • Enter the none keyword to allow the Cisco IP phone to use its own configuration and transmit untagged voice traffic. The router puts the untagged voice traffic into the access VLAN.
  • In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5).
  • Refer to “Configuring PFC QoS,” for information about how to configure QoS.
  • Refer to the “Configuring a LAN Interface as a Layer 2 Access Port” section for information about how to configure the port as a Layer 2 access port and configure the access VLAN.

This example shows how to configure Fast Ethernet port 5/1 to send CDP packets that tell the Cisco IP phone to use VLAN 101 as the voice VLAN:

Router# configure terminal
Router(config)# interface fastethernet 5/1
Router(config-if)# switchport voice vlan 101
Router(config-if)# exit
 

This example shows how to verify the configuration of Fast Ethernet port 5/1:

Router# show interfaces fastethernet 5/1 switchport
Name: Fa5/1
Switchport: Enabled
Administrative Mode: access
Operational Mode: access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: off
Access Mode VLAN: 100
Voice VLAN: 101
Trunking Native Mode VLAN: 1 (default)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: 900 ((Inactive)) 901 ((Inactive))
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Configuring Data Traffic Support

To configure the way in which the Cisco IP phone transmits data traffic, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface fastethernet slot/port

Selects the port to configure.

Step 2

Router(config-if)# mls qos trust extend [ cos cos_value ]

Configures the way in which the Cisco IP phone transmits data traffic.

Router(config-if)# no mls qos trust extend

Clears the configuration.

Step 3

Router(config)# end

Exits configuration mode.

Step 4

Router# show interfaces fastethernet slot/port switchport

Router# show running-config interface fastethernet slot/port

Verifies the configuration.

When configuring the way in which the Cisco IP phone transmits data traffic, note the following information:

  • To send CDP packets that configure the Cisco IP phone to trust tagged traffic received from a device connected to the access port on the Cisco IP phone, do not enter the cos keyword and CoS value.
  • To send CDP packets that configure the Cisco IP phone to mark tagged ingress traffic received from a device connected to the access port on the Cisco IP phone, enter the cos keyword and CoS value (valid values are 0 through 7).
  • You cannot use Cisco IOS software commands to configure whether or not traffic sent from a device attached to the access port on the Cisco IP phone is tagged.

This example shows how to configure Fast Ethernet port 5/1 to send CDP packets that tell the Cisco IP phone to configure its access port as untrusted and to mark all tagged traffic received from a device connected to the access port on the Cisco IP phone with CoS 3:

Router# configure terminal
Router(config)# interface fastethernet 5/1
Router(config-if)# mls qos trust extend cos 3
 

This example shows how to configure Fast Ethernet port 5/1 to send CDP packets that tell the Cisco IP phone to configure its access port as trusted:

Router# configure terminal
Router(config)# interface fastethernet 5/1
Router(config-if)# mls qos trust extend
 

This example shows how to verify the configuration on Fast Ethernet port 5/1:

Router# show queueing interface fastethernet 5/1 | include Extend
Extend trust state: trusted

Configuring Inline Power Support

To configure inline power support, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface fastethernet slot/port

Selects the port to configure.

Step 2

Router(config-if)# power inline { auto | never }

Configures inline power support.

Router(config-if)# no power inline

Clears the configuration.

Step 3

Router(config)# end

Exits configuration mode.

Step 4

Router# show power inline [ fastethernet slot/port ]

Verifies the configuration.

When configuring inline power support, note the following information:

  • To configure auto-detection of a Cisco IP phone, enter the auto keyword.
  • To disable auto-detection of a Cisco IP phone, enter the never keyword.

This example shows how to disable inline power on Fast Ethernet port 5/1:

Router# configure terminal
Router(config)# interface fastethernet 5/1
Router(config-if)# power inline never
 

This example shows how to enable inline power on Fast Ethernet port 5/1:

Router# configure terminal
Router(config)# interface fastethernet 5/1
Router(config-if)# power inline auto
 

This example shows how to verify the inline power configuration on Fast Ethernet port 5/1:

Router# show power inline fastethernet 5/1
Interface Admin Oper Power Device
(Watts)
---------- ----- ---------- ------- -------------------
Fa5/1 auto on 6.3 cisco phone device