Configuring Mutation Mapping

This chapter describes how to configure the mutation of packet values used to define traffic classes on the Cisco NX-OS device. This chapter includes the following sections:

Information About Mutation Mapping

Mutation mapping is a method of modifying a quality of service (QoS) field in all packets on an interface. On ingress, mutation mapping occurs before traffic classification and all other actions. On egress, mutation mapping occurs after traffic classification and before the other actions. You can apply mutation mapping to the class of service (CoS), Differentiated Service Code Point (DSCP), or IP precedence packet fields, or to the internal field discard class.

You cannot configure system-defined mutation maps. You can only configure those maps that modify the same source and destination variable.

You use a hierarchical policy map to configure mutation mapping. In the mutation mapping policy map, you specify the field to mutate and the policy map to apply with the mutation.

Note The device supports hierarchical policies only for mutation mapping.

The sequence of QoS actions on ingress traffic is as follows:

1. Queuing and scheduling

2. Mutation

3. Classification

4. Marking

5. Policing

The sequencing of QoS actions on egress traffic is as follows:

1. Classification

2. Marking

3. Policing

4. Mutation

5. Queuing and scheduling

Note Mutation occurs much closer to the beginning of the traffic actions on the ingress packets, and any further classification and policing is based on the changed QoS values. Mutation occurs at the end of the traffic actions on the egress packets, right before queuing and scheduling.

Licensing Requirements for Mutation Mapping

The following table shows the licensing requirements for this feature:

 

Product
License Requirement

Cisco NX-OS

The QoS feature does not require a license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide .

However, using virtual device contexts (VDCs) requires an Advanced Services license.

Prerequisites for Mutation Mapping

Mutation mapping has the following prerequisites:

  • You must be familiar with Chapter3, “Using Modular QoS CLI”
  • You are logged on to the switch.
  • You are in the VDC. A VDC is a logical representation of a set of system resources. You can use the switchto vdc command with a VDC number.

Guidelines and Limitations

Mutation mapping has the following configuration guidelines and limitations:

  • You use a hierarchical policy for mutation mapping. Hierarchical policies are not supported for any other use.
  • The device supports only one level of hierarchy.
  • You can configure up to 14 table maps for use in ingress interfaces and up to 15 table maps for use in egress interfaces.
  • Before you delete a referenced policy map, you must first remove all references to that policy map.
  • You can use only like parameters (for example, cos-cos) when you create a mutation map. Mutation maps with dissimilar types (for example, cos-dscp) are not supported.

Configuring Mutation Mapping

To configure mutation mapping, you create a hierarchical policy map that uses the class-default traffic class to capture all packets and apply mutation mapping to them. You use the service-policy command to specify the policy map to apply with mutation mapping.

Note You can set only similar values when you create a mutation map. For example, you can set cos-cos or dscp-dscp; you cannot set cos-dscp or dscp-precedence.

To configure mutation mapping, follow these steps:

Step 1 Create the policy map to apply in the mutation mapping hierarchical policy. For information about configuring policy maps, see Chapter 6, “Configuring Policing” or Chapter7, “Configuring Queuing and Scheduling”

Step 2 Create the table map to use in the mutation mapping hierarchical policy. For information about configuring table maps, see the “Configuring Marking Using Table Maps” section.

Step 3 Configure the mutation mapping hierarchical policy as described in this section.

Step 4 Apply the service policy to the interface. For information about attaching policies to interfaces, see Chapter3, “Using Modular QoS CLI”

 

SUMMARY STEPS

1. configure terminal

2. policy-map [ type qos ] [ match-first ] { qos-policy-map-name | qos-dynamic }

3. class class-default

4. set { cos | discard-class | dscp | precedence } { cos | discard-class | dscp | precedence } table table-map-name

5. service-policy [ type qos ] { policy-map-name | qos-dynamic } [ no-stats ]

6. (Optional) show policy-map [ type { qos | queuing }] [ policy-map-name | qos-dynamic]

7. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

configure terminal

 

Example:

switch# configure terminal

switch(config)#

Enters configuration mode.

Step 2

policy-map [ type qos ] [ match-first ] [ qos-policy-map-name | qos-dynamic ]

 

Example:

switch(config)# policy-map policy1

switch(config-pmap-qos)#

Creates or accesses the specified policy map and then enters policy-map mode. The policy map name can contain alphabetic, hyphen, or underscore characters, is case sensitive, and can be up to 40 characters.

Step 3

class class-default

 

Example:

switch(config-pmap-qos)# class class-default

switch(config-pmap-c-qos)#

Configures class-default to capture all traffic in this policy map.

Step 4

set { cos | discard-class | dscp | precedence } { cos | discard-class | dscp | precedence } table table-map-name

 

Example:

switch(config-pmap-c-qos)# set dscp dscp table dscp_mutation

switch(config-pmap-c-qos)#

Sets the first packet field to the value of the second packet field based on the mapping values in the specified table map. For mutation mapping, both fields must have the same value. The specified table map must already exist.

Note You can only set same fields when in mutation mapping (for example, dscp-dscp).

The example shows how to use mutation mapping on the DSCP field based on the mapping values in table map dscp_mutation.

Step 5

service-policy [ type qos ] { policy-map-name | qos-dynamic } [ no-stats ]

 

Example:

switch(config-pmap-c-qos)# service-policy testpolicy

switch(config-pmap-c-qos)#

Defines the policy map to apply with the mutation map. The specified policy map must already exist and cannot contain a service-policy command.

Note Classification within this service policy is based on the mutated value, not on the original value in the packet.

Note The service-policy command can only be used for mutation mapping.

Step 6

show policy-map [type {qos | queuing}] [policy-map-name] | qos-dynamic ]

 

Example:

switch(config-pmap-c-qos)# show policy-map policy1

(Optional) Displays information about all configured policy maps or the specified policy map.

Step 7

copy running-config startup-config

 

Example:

switch(config-pmap-c-qos)# copy running-config startup-config

(Optional) Saves the running configuration to the startup configuration.

Verifying the Mutation Mapping Configuration

To display the mutation mapping configuration information, perform the following tasks:

 

Command
Purpose

show policy-map [ type { qos | queuing }] [ policy-map-name | qos-dynamic ]

Displays information about all configured policy maps or the specified policy map.

For detailed information about the fields in the output from these commands, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x .

Configuration Examples for Mutation Mapping

The following example shows a mutation configuration:

Note If the child service policy (in this example, child_qos_policy) is not configured in the parent policy map (in this example, parent_policy_for_mutation), all packets will be changed according to the mutation map.

class-map type qos match-all dscp0-12
match dscp 0-12
match protocol dhcp
 
class-map type qos match-all dscp13-60
match dscp 13-60
 
table-map mutate_dscp
default copy
from 0 to 0
from 1 to 1
from 2 to 1
from 63 to 46
 
policy-map type qos child_policy
class dscp0-12
police cir 10 mbps bc 200 ms pir 20 mbps be 200 ms conform transmit exceed set dscp dscp table mutate_dscp violate drop
class dscp13-63
police cir 20 mbps bc 200 ms pir 40 mbps be 200 ms conform transmit exceed set dscp dscp table mutate_dscp violate drop
class class-default
police cir 5 mbps bc 200 ms conform transmit violate drop
 
policy-map type qos parent_policy_for_mutation
class class-default
set dscp dscp table mutate_dscp
service-policy type qos child_qos_policy

Feature History for Mutation Mapping

Table 5-1 lists the release history for this feature.

 

Table 5-1 Feature History for Mutation
Feature Name
Releases
Feature Information

No changes from Release 4.1(2)

5.1(1)

—

Mutation Mapping

4.1(2)

You can only use similar variables for mutation mapping.