Specifications

Installation Examples
307
Interface fa0/2 is connected to a MiVoice IP Phone that is capable of sending VLAN tagged
Ethernet frames. When learning the voice VLAN via CDP (as configured), an 802.1p value of
5 is initially assumed. However, if the Mitel proprietary DHCP option 133 is used then this will
overwrite the initial value. Mitel recommends an 802.1p value of 6 (unless using Cisco auto-qos).
By default 802.1p value 6 is a member of queue number 4. This is the expedited queue created
by the priority-queue out command on a Catalyst 3550. This interface configuration assumes
that DHCP option 133 is set to 6. If an alternate value (e.g. 5) is used then the queue members
need further defining.
Interface fa0/24 is the VLAN trunk connection between Switch 2 and Switch 1. For Ethernet
priority information to be sent between the switches the VLAN trunk must be configured.
Ethernet Switch 3 configuration
There are two connections in the example topology for Ethernet Switch 3.
1. Fa0/2 to IP Phone extension 2009
2. Fa0/24 to Router 2 port Fa0/0
In this example VLANs are being assigned to the IP phones using CDP. Configurations for each
port follow (assumes no VTP):
These steps are to set up QoS on the Catalyst 3550 and create the Voice VLAN.
Switch2(config)# interface fa0/24 [the VLAN trunk connection to Switch 1]
Switch2(config-if)# description "Connection to Switch 1"
Switch2(config-if)# switchport trunk encapsulation dot1q [Forces 802.1Q frame]
Switch2(config-if)# switchport mode trunk [sends VLAN information across the link]
Switch2(config-if)# priority-queue out [makes queue 4 a strict priority queue]
Switch3# configure terminal
Switch3(config)# mls qos [sets up QOS on the switch globally]
Switch3(config)# vlan 100 [create the voice VLAN]
Switch3(config-vlan)# name VoiceVLAN [Give it a name]
Switch3(config-vlan)# exit
Switch3(config)# interface fa0/2 [the connection to the ext. 2009]
Switch3(config-if)# description "Connection to
Ext.2009"
Switch3(config-if)# switchport mode access [port defaults to standard Ethernet frame]
Switch3(config-if)# switchport voice vlan 100 [allows the IP set to learn the VLAN via CDP]
Switch3(config-if)# mls qos trust dscp pass-through
cos
[required to allow DSCP & 802.1p through]
Switch3(config-if)# priority-queue out [makes queue 4 a strict priority queue]
Switch3(config-if)# spanning-tree portfast [bypasses the spanning the startup procedure]
Switch3(config-if)# spanning-tree bpdufilter enable [stops spanning tree messages from being sent]