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Note ● For complete syntax and usage information for the commands used in this chapter, see these publications:
http://www.cisco.com/en/US/products/ps11846/prod_command_reference_list.html
http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html
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– 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 contains an integrated 3-port 10/100 switch. The ports are dedicated connections to these devices:
Figure 19-1 shows a Cisco IP phone connected between a switch and a PC.
Figure 19-1 Cisco IP Phone Connected to a Switch
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.
You can configure Layer 2 access ports on the switch to send Cisco Discovery Protocol (CDP) packets that configure an attached Cisco IP phone to transmit voice traffic to the switch in any of the following ways:
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).
To provide more predictable voice traffic flow, you can configure QoS on the switch to trust the Layer 3 IP precedence or Layer 2 CoS value in the received traffic (see Chapter 32, “PFC QoS Overview”).
The trusted boundary device verification feature configures ports on the switch to apply configured QoS port trust commands only when the Cisco Discovery Protocol (CDP) verifies that the device attached to the port is a Cisco IP phone. See the “How to Configure Trusted Boundary with Cisco Device Verification” section.
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.
Note ● The ability to either trust or mark tagged data traffic from the device attached to the access port on the Cisco IP phone is called the “trusted boundary (extended trust for CDP devices)” feature.
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 19-1), you can configure Layer 2 access ports on the switch 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:
Most IP phones have no ability to notify the switch of link state changes on the IP phone’s access port. When a device attached to the access port is disconnected or disabled administratively, the switch is unaware of the change. Some Cisco IP phones can send a CDP message containing a host presence type length value (TLV) indicating the changed state of the access port link.
The switch provides support for authentication, authorization, and accounting (AAA) for Cisco IP phones, as described in Chapter54, “IEEE 802.1X Port-Based Authentication”
The switch also supports automatic tracking for Cisco Emergency Responder (Cisco ER) to help you manage emergency calls in your telephony network. For further information, see this URL:
http://www.cisco.com/en/US/products/sw/voicesw/ps842/tsd_products_support_series_home.html
To configure the way in which the Cisco IP phone transmits voice traffic, perform this task:
When configuring the way in which the Cisco IP phone transmits voice traffic, note the following information:
This example shows how to configure Gigabit Ethernet port 5/1 to send CDP packets that tell the Cisco IP phone to use VLAN 101 as the voice VLAN:
This example shows how to verify the configuration of Gigabit Ethernet port 5/1:
Note The trusted boundary feature is implemented with the platform qos trust extend command.
To configure the way in which an attached Cisco IP phone transmits data traffic, perform this task:
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Router(config-if)# platform qos trust extend [ cos cos_value ] |
Configures the way in which an attached Cisco IP phone transmits data traffic. |
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When configuring the way in which an attached Cisco IP phone transmits data traffic, note the following information:
This example shows how to configure Gigabit 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:
This example shows how to configure Gigabit Ethernet port 5/1 to send CDP packets that tell the Cisco IP phone to configure its access port as trusted:
This example shows how to verify the configuration on Gigabit Ethernet port 5/1:
Note In addition to CDP, you can also use LLDP MED on the port connecting to the Cisco IP Phone to detect and configure it.
http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html
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