Classifying traffic using class of service at the access layer

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Lab 8.9.1 Classifying Traffic using Class of Service at the Access Layer

Objective
For effective quality of service (QoS) it is important to classify traffic as soon as possible. This allows routing and switching processes that can differentiate traffic and provide the required service levels. This lab introduces the use of the Layer 2 class of service (CoS) field as a means of classifyingtraffic entering the network at the access-layer switch. The following key concepts are covered: • • • Trust of an existing CoS, such as provided by an IP phone Manual configuration of CoS for devices incapable of setting it for themselves Manual configuration and overriding the CoS for devices that cannot be trusted

This lab can be performed using the Catalyst 2950 or 3550 switches.Scenario
A company marketing department is expanding and has just obtained some additional floor space for five new staff members. Each staff member has a personal computer and an IP phone. In addition, the marketing department has purchased a video camera so that marketing presentations can be streamed to customers and employees. Configure the access-layer switch for the new workgroup and payparticular attention to their quality of service requirements.

Step 1
If a Catalyst 3550 is being used for this lab, activate the QoS features of the switch from the global configuration mode.

1-5

CCNP 3: Multilayer Switching v 3.0 - Lab 8.9.1

Copyright  2003, Cisco Systems, Inc.

Switch(config)#mls qos

If a Catalyst 2950 is being used for this lab, ignore this step as the QoSfeatures of the 2950 are always available.

Step 2
Configure a Virtual Terminal Protocol (VTP) domain corp and assign VLANs to the interfaces as shown in the topology above.
Switch(config)#vtp domain corp Switch(config)#vtp mode server Switch(config)#interface range fastethernet 0/1 - 6 Switch(config-if-range)#switchport access vlan 10 Switch(config-if-range)#interface range fastethernet 0/7 -11 Switch(config-if-range)#switchport access vlan 20 Switch(config-if-range)#interface fastethernet 0/12 Switch(config-if)#switchport access vlan 30

Step 3
The IP phones have been purchased and have automatically set the Ethernet class of service field to 5. This is an appropriate value. This allows the access-layer switch to pass these Ethernet frames, leaving the CoS intact. In otherwords, the CoS coming in on the IP phone interfaces switch is trusted. Configure interfaces 1 through 6 to trust the incoming CoS.
Switch(config)#interface range fastethernet 0/1 - 6 Switch(config-if-range)#mls qos trust cos

Step 4
The personal computers used in the marketing department do not have any special QoS requirements. By classifying Ethernet frames originating from them with a CoS of0. A best effort delivery priority is represented. Configure interfaces 7 through 11 with a default CoS of 0.
Switch(config)#interface range fastethernet 0/7 – 11 Switch(config-if-range)#mls qos cos 0

Step 5
The personal computers use a network interface card (NIC) that supports 802.1p. Therefore, the PCs have the capability of setting the CoS. The marketing staff would never intentionallywant to disrupt network services. However, if the CoS was set to a high value, data network traffic such as FTP could seriously disrupt voice or video services. Configure interfaces 7 through 11 to override any incoming CoS and set it to the default.
Switch(config-if-range)#mls qos cos override

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CCNP 3: Multilayer Switching v 3.0 - Lab 8.9.1

Copyright  2003, Cisco Systems, Inc. Step 6
The video traffic needs to be given priority treatment within the network. This is because video traffic has different requirements than voice traffic. Assign a separate CoS of 3, which assures the video traffic will be readily identified by other switches and routers within the network. The camera is not capable of setting its own CoS. Configure a default CoS of 3 on interface 12....
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