Configuring Voice VLAN on 3550總結

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Understanding Voice VLAN

The voice VLAN feature enables access ports to carry IP voice traffic from an IP phone. The switch can connect to a Cisco 7960 IP Phone and carry IP voice traffic. Because the sound quality of an IP phone call can deteriorate if the data is unevenly sent, the switch supports quality of service (QoS) based on IEEE 802.1P class of service (CoS). QoS uses classification and scheduling to send network traffic from the switch in a predictable manner. For more information on QoS, see Chapter 29, "Configuring QoS." The Cisco 7960 IP Phone is a configurable device, and you can configure it to forward traffic with an 802.1P priority. You can configure the switch to trust or override the traffic priority assigned by an IP Phone.

The Cisco 7960 IP Phone contains an integrated three-port 10/100 switch as shown in Figure 14-1. The ports provide dedicated connections to these devices:

•Port 1 connects to the switch or other voice-over-IP (VoIP) device.

•Port 2 is an internal 10/100 interface that carries the IP phone traffic.

•Port 3 (access port) connects to a PC or other device.

Figure 14-1 shows one way to connect a Cisco 7960 IP Phone.

Figure 14-1 Cisco 7960 IP Phone Connected to a Switch

When the IP Phone connects to the switch, the access port (PC-to-telephone jack) of the IP phone can connect to a PC. Packets to and from the PC and to or from the IP phone share the same physical link to the switch and the same switch port. For deployment examples that use voice VLANs, refer to the "Network Configuration Examples" section on page 1-9.