Users Guide

794 VLANs

console(config-if-Gi1/0/10)#dot1x port-control mac-based

Enable the Voice VLAN feature on the interface

console(config-if-Gi1/0/10)#switchport voice vlan 25

Disable authentication for the Voice VLAN on the port. This step is

required only if the voice phone does not support port-based

authentication. MAB is not enabled on this port as other devices such as a

PC will still authenticate using 802.1X.

console(config-if-Gi1/0/10)#switchport voice vlan override-

authentication

Exit to Privileged Exec mode.

console(config-if-Gi1/0/10)#<CTRL+Z>

View the Voice VLAN settings for port 10.

console#show voice vlan interface gi1/0/10

Interface............................. Gi1/0/10

Voice VLAN Interface Mode............. Enabled

Voice VLAN ID......................... 25

Voice VLAN COS Override............... False

Voice VLAN DSCP Value................. 46

Voice VLAN Port Status................ Disabled

Voice VLAN Authentication............. Disabled

Enterprise Voice VLAN Configuration With QoS

In this example, Voice VLAN traffic is transmitted and received tagged on

VLAN 25 using IEEE 802.1p user priority 5. Background traffic is carried on

the default VLAN. The 802.1p user priority 5 tagged packets are mapped onto

internal CoS queue 2. CoS queue 2 is additionally configured as strict priority

to ensure that the latency-sensitive voice traffic is transmitted first. This is to

help overcome the quantization effect of IP traffic, where the first voice

sample in an IP packet is typically delayed 10 or 20 ms while the voice

samples are collected. A rate-limiting ACL is applied to ensure that 802.1p

priority 5 packets are limited in their ability to disrupt lower-priority traffic via

a denial-of-service attack.

To configure the switch on the IP phone facing interface:

Create the Voice VLAN.

console#configure

console(config)#vlan 25