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Medianet Campus Cisco Catalyst 3560-X/3750-X QoS Design At-a-Glance

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Medianet Campus Cisco Catalyst 3560-X/3750-X QoS Design

Table Of Contents

Medianet Campus Cisco Catalyst 3560-X/3750-X QoS Design

Role in Medianet Campus Network

QoS Design Steps

Step 1: Globally Enable QoS

Step 2: Configure Ingress QoS Model(s)

Trust DSCP Model

Conditional Trust Model

Service Policy Models

Step 3: Configure Ingress Queuing

Step 4: Configure Egress Queuing

EtherChannel QoS

Cisco Validated Design


Medianet Campus Cisco Catalyst 3560-X/3750-X QoS Design


Role in Medianet Campus Network

The Cisco Catalyst 3560-X & 3750-X series switches are well suited to the role of access switches in medianet campus networks. As such, these switches may connect directly to a variety of endpoints, as well as to distribution-layer switches, as shown in Figure 1.

Figure 1 Cisco Catalyst 3560-X/3750-X Switches in a Medianet Campus Network

QoS Design Steps

There are four main steps to configure QoS on Cisco Catalyst 3560-X and 3750-X series switches:

1. Enable QoS

2. Configure Ingress QoS Model(s):

Trust DSCP Model

Conditional Trust Model

Service Policy Models

3. Configure Ingress Queuing

4. Configure Egress Queuing

Step 1: Globally Enable QoS

QoS is globally enabled on the Cisco Catalyst 3560-X and 3750-X with the mls qos command.

Step 2: Configure Ingress QoS Model(s)

The three most utilized ingress QoS models for medianet campus networks are:

Trust DSCP Model

Conditional Trust Model

Service Policy Models

Combinations of these ingress QoS models may be used at the same time.

Trust DSCP Model

This model is configured with the mls qos trust dscp interface-configuration command.

The Trust DSCP model configures the interface to statically accept and preserve the Layer 3 DSCP markings of all incoming packets. This model is suitable for interfaces connecting to endpoints that can mark DSCP values and are administratively controlled (such as WLAN controllers) as well as for any uplinks to distribution layer switches. Switch ports that can be set to trust DSCP are shown as yellow circles in Figure 1.

Conditional Trust Model

This model is configured with the mls qos trust device interface-configuration command.

The Conditional Trust model configures the interface to dynamically accept markings from endpoints that have met a specific condition (currently based on a successful Cisco Discovery Protocol identification). This model is suitable for switch ports connecting to Cisco IP phones (with the cisco-phone option), Cisco TelePresence Systems (with the cts option), Cisco IP Video Surveillance cameras (with the ip-camera option), and Cisco Digital Media Players (with the media-player option). This model is also suitable for PCs and untrusted devices, since the ports connecting to such devices will remain in their default untrusted state. Switch ports that can be set to conditional trust are shown as green circles in Figure 1.

Service Policy Models

There may be cases where administrators require more detailed or granular policies on their ingress edges and as such they may construct MQC-based policies to implement classification, marking, and/or policing policies. These policies are constructed with:

class-maps which identify the flows using packet markings or by access-lists or other criteria

policy-maps which specify policy actions to be taken on a class-by-class basis

service-policy statements which apply a specific policy-map to an interface(s) and specify direction

Step 3: Configure Ingress Queuing

The medianet ingress queuing model for the Cisco Catalyst 3560-X/3750X is shown in Figure 2.

Figure 2 Catalyst 3560-X/3750-X Ingress Queuing Model

Step 4: Configure Egress Queuing

The medianet egress queuing model for the Cisco Catalyst 3560-X/3750X is shown in Figure 3..

Figure 3 Catalyst 3560-X/3750-X Egress Queuing Model

EtherChannel QoS

QoS policies on the Cisco Catalyst 3560-X/3750-X are configured on the physical port-member interfaces only (and not on the logical Port-Channel interface).

Cisco Validated Design

The Cisco Validated Design for Cisco Catalyst 3650-X and 3750-X series switches in the role of an access switch in a medianet campus network is presented below.

Note: Highlighted commands are interface specific; otherwise these are global.