Configuring Classification

This chapter contains the following sections:

About Classification

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.

You can create class maps to represent each traffic class by matching packet characteristics with the classification criteria in the following table:

Table 1. Classification Criteria

Classification Criteria

Description

CoS

Class of service (CoS) field in the IEEE 802.1Q header.

IP precedence

Precedence value within the type of service (ToS) byte of the IP header.

Differentiated Services Code Point (DSCP)

DSCP value within the DiffServ field of the IP header.

ACL

IP, IPv6, or MAC ACL name.

Packet length

Size range of Layer 3 packet lengths.

IP RTP

Identify applications using Real-time Transport Protocol (RTP) by UDP port number range.

You can specify multiple match criteria, you can choose to not match on a particular criterion, or you can determine the traffic class by matching any or all criteria.


Note

However, if you match on an ACL, no other match criteria, except the packet length, can be specified in a match-all class. In a match-any class, you can match on ACLs and any other match criteria.

Traffic that fails to match any class in a QoS policy map is assigned to a default class of traffic called class-default. The class-default can be referenced in a QoS policy map to select this unmatched traffic.

You can reuse class maps when defining the QoS policies for different interfaces that process the same types of traffic.

Licensing Requirements for Classification

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 NX-OS image 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.

Prerequisites for Classification

Classification has the following prerequisites:

  • You must be familiar with using modular QoS CLI.

  • You are logged on to the device.

Guidelines and Limitations for Classification

Classification has the following guidelines and limitations:

  • A QoS policy that references an ACL that contains a match on a source IPv6 address is not supported. Only matching on IPv4 source/destination and IPv6 destination in supported.

  • A match on CoS/DSCP creates entries for IPv4/IPv6 which requires double the TCAM entries.

  • Port-range matches are LOU expanded on ingress only.

  • MAC address based match is not supported.

  • RTP list not supported as match criteria in class-map for QoS classification.

  • You cannot set both CoS and DSCP values for a class in a policy map.

  • The show commands with the internal keyword are not supported.

  • Matching the packets that are based on DSCP, CoS, or precedence in Cisco Nexus 3400-S switches, the TCAM entries for both IPv4 (single-wide is one entry) and IPv6 (double-wide are two entries) are installed in the hardware. For example, if you match DSCP 4, three entries are installed in the hardware, one entry for IPv4 and two entries for IPv6.

  • You can specify a maximum of 512 match criteria in a class map.

  • You can configure a maximum of 128 classes for use in a single policy map.

  • Packet length classification is not supported.

  • The match-all option in the class-map type qos match-all command is not supported. The match criteria of this command becomes the same as in the class-map type qos match-any command. The class-map type qos match-all command yields the same results as the class-map type qos match-any command.

  • Classification on VLANs is not supported.

  • RTP classification is not supported.

  • QoS classification policies are not supported under system QoS for Layer 2 switch ports. However, you can configure a QoS policy to classify the incoming traffic that is based on CoS/DSCP and map it to different queues. The QoS policy must be applied under all the interfaces that require the classification.

  • MAC-based ACLs are not supported.

Configuring Traffic Classes

Configuring ACL Classification

You can classify traffic by matching packets based on an existing access control list (ACL). Traffic is classified by the criteria defined in the ACL. The permit and deny ACL keywords are ignored in the matching; even though a match criteria in the access-list has a deny action, it is still used for matching for this class.


Note

Use the class-map class_acl command to display the ACL class-map configuration.

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match access-group name acl-name

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_acl

Creates or accesses the class map named class-name and enters class-map mode. The class map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters. (match-any is the default when no option is selected and multiple match statements are entered.)

Step 3

match access-group name acl-name

Example:

switch(config-cmap-qos)# match
access-group name my_acl

Configures the traffic class by matching packets based on the acl-name . The permit and deny ACL keywords are ignored in the matching.

Examples: Configuring ACL Classification

To prevent packets from being matched by the QoS class-map, you must explicitly specify the packets you want to match with permit statements. The implicit default deny statement at the end of the ACL will filter out the remainder. Any explicit deny statements configured inside the access list of a QoS class map will be ignored in the matching and treated as an explicit permit statement as shown in the examples below.

The following examples, A1, B1, and C1, all produce the same QoS matching results:

  • A1
    
ip access-list extended A1
  permit ip 10.1.0.0 0.0.255.255 any
  permit ip 172.16.128.0 0.0.1.255 any
  permit ip 192.168.17.0 0.0.0.255 any
  • B1
    
ip access-list extended B1
  permit ip 10.1.0.0 0.0.255.255 any
  deny ip 172.16.128.0 0.0.1.255 any  /* deny is interpreted as a permit */
  permit ip 192.168.17.0 0.0.0.255 any
  • C1
    
ip access-list extended C1
  deny ip 10.1.0.0 0.0.255.255 any   /* deny is interpreted as a permit */
 deny ip 172.16.128.0 0.0.1.255 any  /* deny is interpreted as a permit */
 deny ip 192.168.17.0 0.0.0.255 any  /* deny is interpreted as a permit */

Adding an explicit DENY ALL at the end of a QoS matching ACL causes the QoS ACL to permit all traffic.

The following examples, D1 and E1, produce the same QoS matching results:

  • D1 
    
ip access-list extended D1
  permit ip 10.1.0.0 0.0.255.255 any
  permit ip 172.16.128.0 0.0.1.255 any
  permit ip 192.168.17.0 0.0.0.255 any
 deny ip 0.0.0.0 255.255.255.255 any  /* deny is interpreted as a permit */

    Note

    The last line in the example effectively becomes a PERMIT ALL statement and results in the QoS ACL to permit all packets.
  • E1
    
ip access-list extended E1
    permit ip 0.0.0.0 255.255.255.255 any

Configuring DSCP Classification

You can classify traffic based on the DSCP value in the DiffServ field of the IP header. The standard DSCP values are listed in the following table:

Table 2. Standard DSCP Values

Value

List of DSCP Values

af11

AF11 dscp (001010)—decimal value 10

af12

AF12 dscp (001100)—decimal value 12

af13

AF13 dscp (001110)—decimal value 14

af21

AF21 dscp (010010)—decimal value 18

af22

AF22 dscp (010100)—decimal value 20

af23

AF23 dscp (010110)—decimal value 22

af31

AF31 dscp (011010)—decimal value 26

af32

AF40 dscp (011100)—decimal value 28

af33

AF33 dscp (011110)—decimal value 30

af41

AF41 dscp (100010)—decimal value 34

af42

AF42 dscp (100100)—decimal value 36

af43

AF43 dscp (100110)—decimal value 38

cs1

CS1 (precedence 1) dscp (001000)—decimal value 8

cs2

CS2 (precedence 2) dscp (010000)—decimal value 16

cs3

CS3 (precedence 3) dscp (011000)—decimal value 24

cs4

CS4 (precedence 4) dscp (100000)—decimal value 32

cs5

CS5 (precedence 5) dscp (101000)—decimal value 40

cs6

CS6 (precedence 6) dscp (110000)—decimal value 48

cs7

CS7 (precedence 7) dscp (111000)—decimal value 56

default

Default dscp (000000)—decimal value 0

ef

EF dscp (101110)—decimal value 46

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match [not] dscp dscp-values
  4. exit
  5. copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_dscp

Creates or accesses the class map named class-name and enters class-map mode. The class-map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters.

Step 3

match [not] dscp dscp-values

Example:

switch(config-cmap-qos)# match dscp af21, af32

Configures the traffic class by matching packets based on dscp-values. The standard DSCP values are shown in the following table.

Use the not keyword to match on values that do not match the specified range.

Step 4

exit

Example:

switch(config-cmap-qos)# exit
switch(config)#

Exits global class-map queuing mode and enters global configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

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

Example

This example shows how to display the DSCP class-map configuration: 

switch# show class-map class_dscp

Configuring IP Precedence Classification

You can classify traffic based on the precedence value in the type of service (ToS) byte field of the IP header. The precedence values are listed in the following:

Table 3. Precedence Values

Value

List of Precedence Values

0-7

IP precedence value

critical

Critical precedence (5)

flash

Flash precedence (3)

flash-override

Flash override precedence (4)

immediate

Immediate precedence (2)

internet

Internetwork control precedence (6)

network

Network control precedence (7)

priority

Priority precedence (1)

routine

Routine precedence (0)

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match [not] precedence precedence-values
  4. exit
  5. copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_ip_precedence

Creates or accesses the class map named class-name and then enters class-map mode. The class-map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters.

Step 3

match [not] precedence precedence-values

Example:

switch(config-cmap-qos)# match precedence 1-2, 5-7

Configures the traffic class by matching packets based on precedence-values . Values are shown in the following table. Use the not keyword to match on values that do not match the specified range.

Step 4

exit

Example:

switch(config-cmap-qos)# exit
switch(config)#

Exits global class-map queuing mode and enters global configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

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

Example

This example shows how to display the IP precedence class-map configuration: 

switch# show class-map class_ip_precedence

Configuring Protocol Classification

For Layer 3 protocol traffic, you can use the ACL classification match.

Table 4. match Command Protocol Arguments

Argument

Description

arp

Address Resolution Protocol (ARP)

bridging

Bridging

cdp

Cisco Discovery Protocol (CDP)

dhcp

Dynamic Host Configuration (DHCP)

isis

Intermediate system to intermediate system (IS-IS)

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match [not] protocol {arp | bridging | cdp | dhcp | isis}
  4. exit
  5. copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_protocol

Creates or accesses the class map named class-name and then enters class-map mode. The class-map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters.

Step 3

match [not] protocol {arp | bridging | cdp | dhcp | isis}

Example:

switch(config-cmap-qos)# match protocol isis

Configures the traffic class by matching packets based on the specified protocol. Use the not keyword to match on protocols that do not match the protocol specified.

Step 4

exit

Example:

switch(config-cmap-qos)# exit
switch(config)#

Exits global class-map queuing mode and enters global configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

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

Example

This example shows how to display the protocol class-map configuration: 

switch# show class-map class_protocol

Configuring CoS Classification

You can classify traffic based on the class of service (CoS) in the IEEE 802.1Q header. This 3-bit field is defined in IEEE 802.1p to support QoS traffic classes. CoS is encoded in the high order 3 bits of the VLAN ID Tag field and is referred to as user_priority.

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match [not] cos cos-list
  4. exit
  5. copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_cos

Creates or accesses the class map named class-name and then enters class-map mode. The class-map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters.

Step 3

match [not] cos cos-list

Example:

switch(config-cmap-qos)# match cos 4,5-6

Configures the traffic class by matching packets based on the list of CoS values. Values can range from 0 to 7. Use the not keyword to match on values that do not match the specified range.

Note 

When a Cisco Nexus Fabric Extender (FEX) is connected and in use, data traffic should not be marked with a CoS value of 7. CoS 7 is reserved for control traffic transiting the Fabric Extender.

Step 4

exit

Example:

switch(config-cmap-qos)# exit
switch(config)#

Exits global class-map queuing mode and enters global configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

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

Example

This example shows how to display the CoS class-map configuration: 

switch# show class-map class_cos

Configuring IP RTP Classification

The IP Real-time Transport Protocol (RTP) is a transport protocol for real-time applications that transmit data such as audio or video and is defined by RFC 3550. Although RTP does not use a common TCP or UDP port, you typically configure RTP to use ports 16384 to 32767. UDP communications uses an even-numbered port and the next higher odd-numbered port is used for RTP Control Protocol (RTCP) communications.


Note

The Cisco Nexus 3400-S switches do not support RTP classification.

You can configure classification based on UDP port ranges, which are likely to target applications using RTP.

SUMMARY STEPS

  1. configure terminal
  2. class-map [type qos] [match-any | match-all] class-name
  3. match [not] ip rtp udp-port-value
  4. exit
  5. copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

class-map [type qos] [match-any | match-all] class-name

Example:

switch(config)# class-map class_rtp

Creates or accesses the class map named class-name and then enters class-map mode. The class-map name can contain alphabetic, hyphen, or underscore characters, and can be up to 40 characters.

Step 3

match [not] ip rtp udp-port-value

Example:

switch(config-cmap-qos)# match ip rtp 2000-2100, 4000-4100

Configures the traffic class by matching packets based on a range of lower and upper UDP port numbers, which is likely to target applications using RTP. Values can range from 2000 to 65535. Use the not keyword to match on values that do not match the specified range.

Step 4

exit

Example:

switch(config-cmap-qos)# exit
switch(config)#

Exits global class-map queuing mode and enters global configuration mode.

Step 5

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

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

Example

This example shows how to display the RTP class-map configuration: 

switch# show class-map class_rtp

Verifying the Classification Configuration

Use the show class-map command to verify the class-map configuration. This command displays all class maps.

Configuration Examples for Classification

The following example shows how to configure classification for two classes of traffic: 

class-map class_dscp
match dscp af21, af32
exit
class-map class_cos
match cos 4, 5-6
exit