QoS Configuration in NX-OS [MQC Explained and Configuration Example]

Cisco Modular QoS CLI (MQC)

Cisco Modular Quality of Service Command Line Interface (MQC) provides a Standard CLI to define and configure QoS policies.

This diagram from CiscoLive illustrate what MQC is about:

The Qos configuration in Nexus 9000 can be achieved in 3 steps:

1. Define traffic classes.
2. Associate policies and actions with each traffic class.
3. Attach policies to logical or physical interfaces.

Class-map

Classification is the separation of packets into traffic classes. You configure the device to take a specific action on the specified classified traffic, such as policing or marking down, or other actions

Cisco

We can use class-map mainly match and then classify traffic based on these parameters:

• CoS
• DSCP
• IP Precedence
• ACL

Configuration Examples:

• Example1: Qos class-map:
  syntax: class-map type qos [match-any | match-all] class-name
  config example: class-map type qos MyClass
  
• Example2: Queuing class-map
  syntax: class-map type qos [match-any | match-all] class-name
  Config example: class-map type queuing match-any c-out-q2
  

Policy-Map

Configure a Policy-map to match on the Class-map and define actions to perform on them: such as marking with DSCP, Cos, setting Qos-class , setting bandwitch, Policing, etc.

Configuration Examples:

• Example1: Qos Policy-map
  syntax: policy-map type qos { [match-first] policy-map-name}
  config example: policy-map type qos MyPolicy
  
• Example2: Queuing policy-map
  syntax: policy-map type queuing [match-any | match-all] class-name
  Config example: policy-map type queuing MyPol_queue

Service-Policy

To attach a policy map to an interface or VLAN, use the service-policy command. It will Apply the specified policy map to input or output packets on the interface.

Configuration Examples:

• Example1: Apply Policy1 on interface 10
  syntax:
  Interface slot/port
  service-policy [type qos] {input | output} {policy-map-name} [no-stats]

Configuration Example

Let’s take first a simple example that will match on Cos 3 and set precedence 5 on the ingress interface Ethernet 1/5:

1- Class-map: Class1:

! create Policy-map Policy1
switch(config)# class-map Class1

! match on cos 3
switch(config-cmap-qos)# match cos 3

2- Policy-map: Policy1:

! create Policy-map Policy1
switch(config)# policy-map policy1

! match on class-map class1:
switch(config-pmap-qos)# class Class1

! setting precedence to 3:
switch(config-pmap-c-qos)# set precedence 3

3– Service-Policy:

interface ethernet 1/5
service-policy input Policy1