The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
This chapter describes how to configure quality of service (QoS) on Cisco Nexus 3000 Series devices. It contains the following sections:
The configurable Cisco NX-OS quality of service (QoS) features allow you to classify the network traffic, prioritize the traffic flow, and provide congestion avoidance.
The default QoS configuration on the device provides best-effort service for Ethernet traffic. QoS can be configured to provide additional classes of service for Ethernet traffic. Cisco NX-OS QoS features are configured using Cisco Modular QoS CLI (MQC).
Note |
In the event of congestion or collisions, Ethernet will drop packets. The higher level protocols detect the missing data and retransmit the dropped packets. |
The Cisco Modular QoS CLI (MQC) provides a standard set of commands for configuring QoS.
You can use MQC to define additional traffic classes and to configure QoS policies for the whole system and for individual interfaces. Configuring a QoS policy with MQC consists of the following steps:
MQC provides two command types to define traffic classes and policies:
Defines a class map that represents a class of traffic based on packet-matching criteria. Class maps are referenced in policy maps.
The class map classifies incoming packets based on matching criteria, such as the IEEE 802.1p CoS value. Unicast and multicast packets are classified.
—Defines a policy map that represents a set of policies to be applied on a class-by-class basis to class maps.
The policy map defines a set of actions to take on the associated traffic class, such as limiting the bandwidth or dropping packets.
You define the following class-map and policy-map object types when you create them:
Defines MQC objects that you can use for system level related actions.
Defines MQC objects that you can use for classification.
Defines MQC objects that you can use for queuing and scheduling.
Note |
The qos type is the default for the class-map and policy-map commands, but not for the service-policy which requires that you specify an explicit type. |
You can attach policies to interfaces or EtherChannels as well as at the global system level by using the service-policy command.
You can view all or individual values for MQC objects by using the show class-map and show policy-map commands.
An MQC target is an entity (such as an Ethernet interface) that represents a flow of packets. A service policy associates a policy map with an MQC target and specifies whether to apply the policy on incoming or outgoing packets. This mapping enables the configuration of QoS policies such as marking, bandwidth allocation, buffer allocation, and so on.
The system qos is a type of MQC target. You use a service-policy to associate a policy map with the system qos target. A system qos policy applies to all interfaces on the switch unless a specific interface has an overriding service-policy configuration. The system qos policies are used to define system classes, the classes of traffic across the entire switch, and their attributes. To ensure QoS consistency (and for ease of configuration), the switch distributes the system class parameter values to all its attached network adapters using the Data Center Bridging Exchange (DCBX) protocol.
If service policies are configured at the interface level, the interface-level policy always takes precedence over system class configuration or defaults.
On the Cisco Nexus 3000 Series switch, a system class is uniquely identified by a qos-group value. A total of eight system classes are supported. The Cisco Nexus 3000 Series switch supports one default class which is always present on the switch. Up to seven additional system classes can be created by the administrator.
The switch provides the following system classes:
The switch supports a number of policy types. You create class maps in the policy types.
There are three policy types. The following QoS parameters can be specified for each type of class:
Note |
A network-qos policy can only be attached to the system qos target. |
Note |
Cisco Nexus 3000 Series supports one MTU for all classes for all ports. |
Note |
Enabling WRED/ECN on a class on a network-qos policy implies that WRED/ECN is enabled for all ports in the system. |
Note |
Some configuration parameters when applied to an EtherChannel are not reflected on the configuration of the member ports. |
Note |
These policies can be attached to the system qos target or to any interface. The output queuing policy is used to configure output queues on the switch associated with system classes. |
Note |
Some configuration parameters when applied to an EtherChannel are not reflected on the configuration of the member ports. |
Note |
This policy can be attached to the system or to any interface. It applies to input traffic only. |
The trust boundary is enforced by the incoming interface as follows:
After the system applies the untagged CoS value, QoS functions the same as for a packet that entered the system tagged with the CoS value.
You use classification to partition traffic into classes. You classify the traffic based on the port characteristics (CoS field) or the packet header fields that include IP precedence, Differentiated Services Code Point (DSCP), and Layer 2 to Layer 4 parameters. The values used to classify traffic are called match criteria. When you define a traffic class, you can specify multiple match criteria or you can determine the traffic class by matching any or all criteria.
Traffic that fails to match any class is assigned to a default class of traffic called class-default.
You can associate an egress policy map with an Ethernet interface to guarantee the bandwidth for the specified traffic class or to configure the egress queues.
The bandwidth allocation limit applies to all traffic on the interface.
Each Ethernet interface supports up to six queues, one for each system class. The queues have the following default configuration:
If you add a system class, a queue is assigned to the class. You must reconfigure the bandwidth allocation on all affected interfaces. Bandwidth is not dedicated automatically to user-defined system classes.
You can configure a strict priority queue. This queue is serviced before all other queues except the control traffic queue (which carries control rather than data traffic).
The device automatically applies QoS policies to traffic that is directed to the CPU to ensure that the CPU is not flooded with packets. Control traffic, such as bridge protocol data units (BPDU) frames, is given higher priority to ensure delivery.
To maintain optimal switch performance, follow these guidelines when configuring system classes and policies:
When configuring EtherChannels, note the following guidelines:
Configuring System Classes
You can create or modify a class map with the class-map command. The class map is a named object that represents a class of traffic. In the class map, you specify a set of match criteria for classifying the packets. You can then reference class maps in policy maps.
Note |
The class map type default is type qos and its match criteria default is match-all. |
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 if a match criteria in the access-list has a deny action, it is still used for matching for this class.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
||
Step 2 | switch(config)# class-map type qos class-name |
Creates a named object that represents a class of traffic. Class-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
||
Step 3 | switch(config-cmap-qos)# match access-group name acl-name |
Configures a traffic class by matching packets based on the acl-name. The permit and deny ACL keywords are ignored in the matching.
|
||
Step 4 | switch(config-cmap-qos)# no match access-group name acl-name |
(Optional) Removes the match from the traffic class. |
This example shows how to classify traffic by matching packets based on existing ACLs:
switch# configure terminal
switch(config)# class-map type qos class_acl
switch(config-cmap-qos)# match access-group name acl-01
Use the show class-map command to display the ACL class-map configuration:
switch# show class-map class_acl
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.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
Step 2 | switch(config)# class-map type qos class-name |
Creates a named object that represents a class of traffic. Class-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
Step 3 | switch(config-cmap-qos)# match cos cos-value |
Specifies the CoS value to match for classifying packets into this class. You can configure a CoS value in the range of 0 to 7. |
Step 4 | switch(config-cmap-qos)# no match cos cos-value |
(Optional) Removes the match from the traffic class. |
This example shows how to classify traffic by matching packets based on a defined CoS value:
switch# configure terminal switch(config)# class-map type qos match-any class_cos switch(config-cmap-qos)# match cos 4, 5-6
Use the show class-map command to display the CoS value class-map configuration:
switch# show class-map class_cos
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 |
AF32 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 |
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
Step 2 | switch(config)# class-map type qos class-name |
Creates a named object that represents a class of traffic. Class-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
Step 3 | switch(config-cmap-qos)# match dscp dscp-list |
Configures the traffic class by matching packets based on the values in the dscp-list variable. For a list of DSCP values, see the Standard DSCP Values table. |
Step 4 | switch(config-cmap-qos)# no match dscp dscp-list |
(Optional) Removes the match from the traffic class. For a list of DSCP values, see the Standard DSCP Values table. |
This example shows how to classify traffic by matching packets based on the DSCP value in the DiffServ field of the IP header:
switch# configure terminal switch(config)# class-map type qos match-any class_dscp switch(config-cmap-qos)# match dscp af21, af32
Use the show class-map command to display the DSCP class-map configuration:
switch# show class-map class_dscp
The IP Real-time Transport Protocol (RTP) is a transport protocol for real-time applications that transmits 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 use an even port and the next higher odd port is used for RTP Control Protocol (RTCP) communications.
You can classify based on UDP port ranges, which are likely to target applications using RTP.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
Step 2 | switch(config)# class-map type qos class-name |
Creates a named object that represents a class of traffic. Class-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
Step 3 | switch(config-cmap-qos)# match ip rtp port-number |
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. |
Step 4 | switch(config-cmap-qos)# no match ip rtp port-number |
(Optional) Removes the match from the traffic class. |
This example shows how to classify traffic by matching packets based on UDP port ranges that are typically used by RTP applications:
switch# configure terminal switch(config)# class-map type qos match-any class_rtp switch(config-cmap-qos)# match ip rtp 2000-2100, 4000-4100
Use the show class-map command to display the RTP class-map configuration:
switch# show class-map class_rtp
You can classify traffic based on the precedence value in the type of service (ToS) byte field of the IP header (either IPv4 or IPv6). The following table shows the 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) |
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
Step 2 | switch(config)# class-map type qos match-any class-name | Creates a named object that represents a class of traffic. Class-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
Step 3 | switch(config-cmap-qos)#match precedence precedence-values | Configures the traffic class by matching packets based on precedence values. For a list of precedence values, see the Precedence Values table. |
Step 4 | switch((config-cmap-qos)# no match precedence precedence-values | (Optional) Removes the match from the traffic class. For a list of precedence values, see the Precedence Values table. |
This example shows how to classify traffic by matching packets based on the precedence value in the ToS byte field of the IP header:
switch# configure terminal switch(config)# class-map type qos match-any class_precedence switch(config-cmap-qos)# match precedence 1-2, critical
Use the show class-map command to display the IP precedence value class-map configuration:
switch# show class-map class_precedence
The policy-map command is used to create a named object that represents a set of policies that are to be applied to a set of traffic classes.
The switch provides one default system class: a drop class for best-effort service (class-default). You can define up to four additional system classes for Ethernet traffic.
The following predefined policy maps are used as default service policies:
You need to create a policy map to specify the policies for any user-defined class. In the policy map, you can configure the QoS parameters for each class. You can use the same policy map to modify the configuration of the default classes.
The switch distributes all the policy-map configuration values to the attached network adapters.
Before creating the policy map, define a class map for each new system class.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
||
Step 2 | switch(config)# policy-map [type {network-qos | qos | queuing}] policy-name |
Creates a named object representing a set of policies that are to be applied to a set of traffic classes. Policy-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. The three policy-map configuration modes are as follows: |
||
Step 3 | switch(config)# no policy-map [type {network-qos | qos | queuing}] policy-name |
(Optional) Deletes the specified policy map. |
||
Step 4 | switch(config-pmap)# class [type {network-qos | qos | queuing}] class-name |
Associates a class map with the policy map, and enters configuration mode for the specified system class. The three class-map configuration modes are as follows:
|
||
Step 5 | switch(config-pmap)# no class [type {network-qos | qos | queuing}] class-name |
(Optional) Deletes the class map association. |
Type qos policies are used for classifying the traffic of a specific system class identified by a unique qos-group value. A type qos policy can be attached to the system or to individual interfaces for ingress traffic only.
You can set a maximum of five qos groups for ingress traffic.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
||
Step 2 | switch(config)# policy-map type qos policy-name | Creates a named object that represents a set of policies that are to be applied to a set of traffic classes. Policy-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
||
Step 3 | switch(config-pmap-qos)# class type qos class-name | Associates a class map with the policy map, and enters configuration mode for the specified system class.
|
||
Step 4 | switch(config-pmap-c-qos)# set qos-group qos-group-value | Configures one or more qos-group values to match on for classification of traffic into this class map. The list below identifies the ranges of the qos-group-value . There is no default value.
|
||
Step 5 | switch(config-pmap-c-qos)# no set qos-group qos-group-value | (Optional) Removes the qos-group values from this class. |
This example shows how to define a type qos policy map:
switch# configure terminal switch(config)# policy-map type qos policy-s1 switch(config-pmap-qos)# class type qos class-s1 switch(config-pmap-c-qos)# set qos-group 2
Type network qos policies can only be configured on the system qos attachment point. They are applied to the entire switch for a particular class.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
||
Step 2 | switch(config)# policy-map type network-qos policy-name |
Creates a named object that represents a set of policies that are to be applied to a set of traffic classes. Policy-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
||
Step 3 | switch(config-pmap-nq)# class type network-qos class-name |
Associates a class map with the policy map, and enters configuration mode for the specified system class.
|
||
Step 4 | switch(config-pmap-c-nq)# mtu mtu-value |
Specifies the MTU value in bytes.
|
||
Step 5 | switch(config-pmap-c-nq)# no mtu |
(Optional) Resets the MTU value in this class. |
||
Step 6 | switch(config-pmap-c-nq)# congestion-control random-detect |
(Optional) Configure congestion avoidance with WRED in egress policy maps. By default, tail-drop is the congestion control mechanism.. |
||
Step 7 | switch(config-pmap-c-nq)# congestion-control random-detect ecn |
(Optional) Marks packets instead of dropping them when the average queue length exceeds a specific threshold value. Routers and end hosts use this marking as a signal that the network is congested to slow down sending packets. |
||
Step 8 | switch(config-pmap-c-nq)# set cos cos-value |
Specifies a 802.1Q CoS value which is used to mark packets on this interface. The value range is from 0 to 7. |
||
Step 9 | switch(config-pmap-c-nq)# no set cos cos-value |
(Optional) Disables the marking operation in this class. |
This example shows how to define a type network-qos policy map:
switch# configure terminal switch(config)# policy-map type network-qos policy-que1 switch(config-pmap-nq)# class type network-qos class-que1 switch(config-pmap-c-nq)# mtu 5000 switch(config-pmap-c-nq)# set cos 4
Type queuing policies are used for scheduling and buffering the traffic of a specific system class. A type queuing policy is identified by its qos-group and can be attached to the system or to individual interfaces for input or output traffic.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
||
Step 2 | switch(config)# policy-map type queuing policy-name |
Creates a named object that represents a set of policies that are to be applied to a set of traffic classes. Policy-map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters. |
||
Step 3 | switch(config-pmap-que)# class type queuing class-name |
Associates a class map with the policy map, and enters configuration mode for the specified system class. |
||
Step 4 | switch(config-pmap-c-que)# bandwidth percent percentage |
Specifies the guaranteed percentage of interface bandwidth allocated to this class. By default, no bandwidth is specified for a class.
|
||
Step 5 | switch(config-pmap-c-que)# no bandwidth percent percentage |
(Optional) Removes the bandwidth specification from this class. |
||
Step 6 | switch(config-pmap-c-que)# priority |
Specifies that traffic in this class is mapped to a strict priority queue.
|
||
Step 7 | switch(config-pmap-c-que)# no priority |
(Optional) Removes the strict priority queuing from the traffic in this class. |
This example shows how to define a type queuing policy map:
switch# configure terminal switch(config)# policy-map type queuing policy-queue1 switch(config-pmap-que)# class type queuing class-queue1 switch(config-pmap-c-que)# bandwidth 20
Marking is a method that you use to modify the QoS fields of the incoming and outgoing packets. The QoS fields that you can mark are CoS, IP precedence, and Differentiated Service Code Point (DSCP).
You can use marking commands in traffic classes that are referenced in a policy map. The marking features that you can configure are listed below:
The value of the CoS field is recorded in the high-order three bits of the VLAN ID Tag field in the IEEE 802.1Q header.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
||
Step 2 | switch(config) # policy-map [type network-qos] policy-map name |
Creates or accesses the policy map named policy-map-name and 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 | switch(config-pmap-nq) # class [type network-qos] {class-map name |class-default} |
Creates a reference to class-map-name and enters policy-map class configuration mode. Use the class-default keyword to select all traffic that is not currently matched by classes in the policy map. |
||
Step 4 | switch(config-pmap-c-nq) # set cos cos-value |
Specifies the CoS value to cos-value. The cos-value can range from 0 to 7.
|
You can set the DSCP value in the six most significant bits of the DiffServ field of the IP header to a specified value. You can enter numeric values from 0 to 60, in addition to the standard DSCP values shown in the table below:
Note |
You can set DSCP or IP Precedence but you can not set both values because they modify the same field in the IP packet. |
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 |
Command or Action | Purpose | |
---|---|---|
Step 1 | config t |
Enters configuration mode. |
Step 2 | policy-map type qos qos-policy-map-name |
Creates or accesses the policy map named policy-map-name, 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 [type qos] {class-map-name | class-default} |
Creates a reference to class-map-name, and enters policy-map class configuration mode. Use the class-default keyword to select all traffic that is not currently matched by classes in the policy map. |
Step 4 | set dscp dscp-value |
Sets the DSCP value to dscp-value. See the Standards DSCP Values table. |
This example shows how to display the policy-map configuration as shown below:
switch# show policy-map policy1
You can set the value of the IP precedence field in bits 0 to 2 of the IPv4 type of service (ToS) field or the equivalent Traffic Class field for IPv6 of the IP header. The following table shows the precedence values:
Note |
You can set IP Precedence or DSCP but you can not set both values because they modify the same field in the IP packet. |
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) |
Command or Action | Purpose | |
---|---|---|
Step 1 | config t |
Enters configuration mode. |
Step 2 | policy-map [type qos] qos-policy-map-name |
Creates or accesses the policy map named policy-map-name, 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 [type qos] {class-map-name | class-default} |
Creates a reference to class-map-name, and enters policy-map class configuration mode. Use the class-default keyword to select all traffic that is not currently matched by classes in the policy map. |
Step 4 | set precedence precedence-value |
Sets the IP precedence value to precedence-value. You can enter one of the values shown in the Precedence Values table. |
switch(config)# policy-map type qos my_policy switch(config-pmap-qos)# class type qos my_class switch(config-pmap-c-qos)# set precedence 5 switch(config-pmap-c-qos)#
QoS Configurations for Layer 3 Routing
In Layer 3 topologies, you must configure each qos-group in the network-qos policy with a unique cos value.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# show policy-map system | Displays the already configured policy-maps and CoS values. In Layer 3 topologies, each qos-group must have a unique CoS value. Use the show policy-map system command to view CoS values that have been used and that are unavailable for qos-groups. |
||
Step 2 | switch# configure terminal | Enters global configuration mode. |
||
Step 3 | switch(config) # policy-map [type network-qos] policy-map name | Creates or accesses the policy map named policy-map-name and 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 4 | switch(config-pmap-nq) # class [type network-qos] {class-map name |class-default} | Creates a reference to class-map-name and enters policy-map class configuration mode. Use the class-default keyword to select all traffic that is not currently matched by classes in the policy map. |
||
Step 5 | switch(config-pmap-nq-c) # set cos cos-value | Specifies the CoS value. The value can range from 0 to 7.
|
The following example shows how to set the CoS value to 4 in a Layer 3 topology:
switch# show policy-map system Type network-qos policy-maps =============================== policy-map type network-qos pn-01 class type network-qos cn-01 match qos-group 1 mtu 8500 pause no-drop set cos 2 class type network-qos cn-02 match qos-group 2 set cos 4 mtu 9216 class type network-qos cn-03 match qos-group 3 mtu 8000 set cos 6 class type network-qos cn-04 match qos-group 4 mtu 8750 set cos 7 class type network-qos cn-ip-multicast match qos-group 5 set cos 5 mtu 7500 class type network-qos class-default match qos-group 0 mtu 1500 multicast-optimize set cos 1 ... switch# configure terminal switch(config)# policy-map type network-qos pn-01 switch(config-pmap-nq)# class type network-qos cn-05 switch(config-pmap-c-nq)# set cos 3
You can map CoS values to an egress queue. You can have a maximum of 4 multicast queues for Layer 3 multicast traffic.
You can use this procedure to distribute traffic into different queues, where each queue is configured with different weighted round robin (WRR) parameters.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
Step 2 | switch(config)# wrr-queue qos-group-map queue-id group1 ...group8 |
Maps the assigned CoS values to an egress queue. The egress queue range is from 1 to 4, where 4 can be configured as the expedite queue. You can enter up to eight CoS values. Separate each value with a space. The range is from 0 to 7. |
This example shows how to configure a Layer 3 interface:
switch# configure terminal switch(config)# wrr-queue qos-group-map 1 5 switch(config)#
You can configure a service policy to a Layer 3 interface.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
||
Step 2 | switch(config)# interface ethernet slot/port |
Enters configuration mode for the specified interface. |
||
Step 3 | switch(config-if)# no switchport |
Selects the Layer 3 interface. |
||
Step 4 | switch(config-if)# service-policy [type {qos | queuing output}policy-name |
Specifies the policy map to use as the service policy for the Layer 3 interface. There are two policy-map configuration modes:
|
This example shows how to attach a queuing policy map to a Layer 3 interface:
switch# configure terminal switch(config)# interface ethernet 1/5 switch(config-if)# no switchport switch(config-if)# service-policy type queuing output my_output_q_policy switch(config-if)#
You can change the bandwidth allocated to unicast and multicast traffic by assigning weighted round robin (WRR) weights as a percentage of the interface data rate to the egress queues.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
Step 2 | switch(config)# interface ethernet slot/port |
Enters configuration mode for the specified interface. |
Step 3 | switch(config-if)# wrr unicast-bandwidth percentage-value |
Changes the bandwidth allocated to unicast and multicast traffic on traffic congestion. The percent bandwidth value ranges from 0 to 100 percent. |
This example shows how to attach a queuing policy map to a Layer 3 interface:
switch# configure terminal switch(config)# interface ethernet 1/5 switch(config-if)# wrr unicast-bandwidth 75 switch(config-if)#
The service-policy command specifies the system class policy map as the service policy for the system.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
||
Step 2 | switch(config)# system qos |
Enters system class configuration mode. |
||
Step 3 | switch(config-sys-qos)# service-policy type {network-qos [input | output] | qos input |queuing output} policy-name |
Specifies the policy map to use as the service policy for the system. There are three policy-map configuration modes:
|
This example shows how to set a no-drop Ethernet policy map as the system class:
If you have created and attached new policies to the system QoS configuration, enter the no form of the command to reapply the default policies.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal | Enters global configuration mode. |
Step 2 | switch(config)# system qos |
Enters system class configuration mode. |
Step 3 | switch(config-sys-qos)# no service-policy type qos input policy-map name |
Resets the classification mode policy map. This policy-map configuration is for system QoS input or interface input only: |
Step 4 | switch(config-sys-qos)# no service-policy type network-qos policy-map name |
Resets the network-wide policy map. |
Step 5 | switch(config-sys-qos)# no service-policy type queuing output policy-map name |
Resets the output queuing mode policy map. |
This example shows how to reset the system QoS configuration:
switch# configure terminal switch(config)# system qos switch(config-sys-qos)# no service-policy type qos input my-in-policy switch(config-sys-qos)# no service-policy type network-qos my-nq-policy switch(config-sys-qos)# no service-policy type queuing output my-out-policy
This example shows the default service policies:
You can enable the jumbo MTU for the whole switch by setting the MTU to its maximum size (9216 bytes) in the policy map for the default Ethernet system class (class-default).
Note |
The Cisco Nexus 3000 Series supports 1 MTU for all classes for all ports. |
This example shows how to configure the default Ethernet system class to support the jumbo MTU:
switch(config)# policy-map type network-qos jumbo switch(config-pmap-nq)# class type network-qos class-default switch(config-pmap-c-nq)# mtu 9216 switch(config-pmap-c-nq)# exit switch(config-pmap-nq)# exit switch(config)# system qos switch(config-sys-qos)# service-policy type network-qos jumbo
Note |
The system jumbomtu command defines the maximum MTU size for the switch. However, jumbo MTU is only supported for system classes that have MTU configured. |
To verify that the jumbo MTU is enabled, enter the show interface ethernet slot/port command for an Ethernet interface that carries traffic with jumbo MTU.
This example shows how to display summary jumbo MTU information for Ethernet 1/2 (the relevant part of the output is shown in bold font):
switch# show interface ethernet 1/2 Ethernet1/2 is up ... Rx 1547805598 Input Packets 1547805596 Unicast Packets 0 Multicast Packets 0 Broadcast Packets 1301767362 Jumbo Packets 33690 Storm Suppression Packets 7181776513802 Bytes Tx 1186564478 Output Packets 7060 Multicast Packets 0 Broadcast Packets 997813205 Jumbo Packets 4813632103603 Bytes ......
This example shows how to display detailed jumbo MTU information for Ethernet 1/2 (the relevant part of the output is shown in bold font):
switch# show interface ethernet 1/2 counters detailed Rx Packets: 1547805598 Rx Unicast Packets: 1547805596 Rx Jumbo Packets: 1301767362 Rx Bytes: 7181776513802 Rx Storm Suppression: 33690 Rx Packets from 0 to 64 bytes: 169219 Rx Packets from 65 to 127 bytes: 10657133 Rx Packets from 128 to 255 bytes: 21644488 Rx Packets from 256 to 511 bytes: 43290596 Rx Packets from 512 to 1023 bytes: 86583071 Rx Packets from 1024 to 1518 bytes: 83693729 Rx Trunk Packets: 1547805596 Tx Packets: 1186564481 Tx Unicast Packets: 1005445334 Tx Multicast Packets: 7063 Tx Jumbo Packets: 997813205 Tx Bytes: 4813632103819 Tx Packets from 0 to 64 bytes: 137912 Tx Packets from 65 to 127 bytes: 8288443 Tx Packets from 128 to 255 bytes: 16596457 Tx Packets from 256 to 511 bytes: 33177999 Tx Packets from 512 to 1023 bytes: 66363944 Tx Packets from 1024 to 1518 bytes: 64186521 Tx Trunk Packets: 1005451729
Configuring QoS on Interfaces
Any incoming packet not tagged with an 802.1p CoS value is assigned the default untagged CoS value of zero (which maps to the default Ethernet drop system class). You can override the default untagged CoS value for an Ethernet or EtherChannel interface.
Command or Action | Purpose | |
---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
Step 2 | switch(config)# interface {ethernet [chassis/]slot/port | port-channel channel-number} |
Enters configuration mode for the specified interface or port channel. |
Step 3 | switch(config-if)# no switchport |
(Optional) Selects a Layer 3 interface. |
Step 4 | switch(config-if)# untagged cos cos-value |
Configures the untagged CoS value. Values can be from 1 to 7. |
This example shows how to set the CoS value to 4 for untagged frames received on an interface:
switch# configure terminal switch(config)# interface ethernet 1/2 switch(config-if)# untagged cos 4
This example shows how to set the CoS value to 3 for untagged frames received on a Layer 3 interface:
switch# configure terminal switch(config)# interface ethernet 1/5 switch(config-if)# no switchport switch(config-if)# untagged cos 3 switch(config-if)#
An input qos policy is a service policy applied to incoming traffic on an Ethernet interface for classification. For type queuing, the output policy is applied to all outgoing traffic that matches the specified class.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | switch# configure terminal |
Enters configuration mode. |
||
Step 2 | switch(config)# interface {ethernet [chassis/]slot/port | port-channel channel-number} |
Enters configuration mode for the specified interface.
|
||
Step 3 | switch(config-if)# service-policy [type {qos input | queuing output}] policy-name |
Specifies the policy map to use as the service policy for the system. There are two policy-map configuration modes:
|
||
Step 4 | switch(config-if)# service-policy input policy-name |
Applies the policy map to the interface.
|
This example shows how to apply a policy to an Ethernet interface:
switch# configure terminal
switch(config)# interface ethernet 1/1
switch(config-if)# service-policy type qos input policy1
To verify Cisco Nexus 3000 Series QoS configurations, perform one of these tasks:
Command |
Purpose |
---|---|
switch# show class-map | Displays the class maps defined on the switch. |
switch# show policy-map [name] | Displays the policy maps defined on the switch. Optionally, you can display the named policy only. |
switch# show policy-map interface [interface number] | Displays the policy map settings for an interface or all interfaces. |
switch# show policy-map system | Displays the policy map settings attached to the system qos. |
switch# show policy-map type {network-qos | qos | queuing} [name] | Displays the policy map settings for a specific policy type. Optionally, you can display the named policy only. |
switch# show interface untagged-cos [ module number] | Displays the untagged CoS values for all interfaces. |
switch# show wrr-queue cos-map [var] | Displays the mapped CoS values to egress queues. |
switch# running-config ipqos | Displays information about the running configuration for QoS. |
switch# startup-config ipqos | Displays information about the startup configuration for QoS. |
switch# show queuing interface ethernet slot-no/port-no | Displays the queuing information on interfaces. |
This example shows how to configure a network qos policy:
switch(config)# class-map type network-qos cnq1 switch(config-cmap-nq)# match qos-group 1 switch(config-cmap-nq)# exit switch(config)# class-map type network-qos cnq6 switch(config-cmap-nq)# match qos-group 6 switch(config-cmap-nq)# switch(config-cmap-nq)# exit switch(config)# policy-map type network-qos pnqos switch(config-pmap-nq)# class type network-qos cnq1 switch(config-pmap-nq-c)# set cos 4 switch(config-pmap-nq-c)# exit switch(config-pmap-nq)# class type network-qos cnq6 switch(config-pmap-nq-c)# set cos 5 switch(config-pmap-nq-c)# congestion-control random-detect ecn switch(config-pmap-nq-c)# exit switch(config-pmap-nq)# class type network-qos class-default switch(config-pmap-nq-c)# mtu 9216 switch(config-pmap-nq-c)# exit switch(config-pmap-nq)# exit switch(config)# system qos switch(config-sys-qos)# service-policy type network-qos pnqos switch(config-sys-qos)#
This example shows how to configure a queuing policy:
switch(config)# class-map type queuing cqu1 switch(config-cmap-que)# match qos-group 1 switch(config-cmap-que)# exit switch(config)# class-map type queuing cqu6 switch(config-cmap-que)# match qos-group 6 switch(config-cmap-que)# exit switch(config)# policy-map type queuing pqu switch(config-pmap-que)# class type queuing class-default switch(config-pmap-c-que)# bandwidth percent 70 switch(config-pmap-c-que)# exit switch(config-pmap-que)# class type queuing cqu1 switch(config-pmap-c-que)# bandwidth percent 10 switch(config-pmap-c-que)# exit switch(config-pmap-que)# class type queuing cqu6 switch(config-pmap-c-que)# bandwidth percent 20 switch(config-pmap-c-que)# exit switch(config-pmap-que)# exit switch(config)# system qos switch(config-sys-qos)# service-policy type queuing output pqu switch(config-sys-qos)#
This example shows how to configure a QoS policy:
switch(config)# class-map type qos cqos1 switch(config-cmap-qos)# match cos 1 switch(config-cmap-qos)# exit switch(config)# class-map type qos cqos6 switch(config-cmap-qos)# match cos 6 switch(config-cmap-qos)# exit switch(config)# policy-map type qos pqos switch(config-pmap-qos)# class type qos cqos1 switch(config-pmap-c-qos)# set qos-group 1 switch(config-pmap-c-qos)# exit switch(config-pmap-qos)# class type qos cqos6 switch(config-pmap-c-qos)# set qos-group 6 switch(config-pmap-c-qos)# exit switch(config-pmap-qos)# exit switch(config)# system qos switch(config-sys-qos)# service-policy type qos input pqos switch(config-sys-qos)#
This example shows how to verify the untagged-cos configuration on interfaces:
switch(config-if)# show interface untagged-cos ================================= Interface Untagged-CoS ================================= Ethernet1/1 4 Ethernet1/2 Ethernet1/3 5 Ethernet1/4 Ethernet1/5 Ethernet1/6 Ethernet1/7 Ethernet1/8 Ethernet1/9 Ethernet1/10 Ethernet1/11 Ethernet1/12 Ethernet1/13 Ethernet1/14 Ethernet1/15 Ethernet1/16 Ethernet1/17
This example shows how to display the Qos running configuration:
switch(config)# show running-config ipqos !Command: show running-config ipqos !Time: Mon Mar 15 08:24:12 2010 version 5.0(3)U1(1) class-map type qos match-all cqos1 match cos 1 class-map type qos match-all cqos6 match cos 6 class-map type queuing cqu1 match qos-group 1 class-map type queuing cqu6 match qos-group 6 policy-map type qos pqos class cqos1 set qos-group 1 class cqos6 set qos-group 6 policy-map type queuing pqu class type queuing cqu1 bandwidth percent 10 class type queuing cqu6 bandwidth percent 20 class type queuing class-default bandwidth percent 70 class-map type network-qos cnq1 match qos-group 1 class-map type network-qos cnq6 match qos-group 6 policy-map type network-qos pnqos class type network-qos cnq1 set cos 4 class type network-qos cnq6 set cos 5 congestion-control random-detect ecn class type network-qos class-default mtu 9216 system qos service-policy type qos input pqos service-policy type network-qos pnqos service-policy type queuing output pqu interface Ethernet1/1 untagged cos 4 interface Ethernet1/3 untagged cos 5 switch(config)#
This example shows how to display the QoS groups that are mapped to the egress queue:
switch(config)# wrr-queue qos-group-map 3 1 switch(config)# show wrr-queue qos-group-map MCAST Queue ID Qos-Group Map 0 0 1 2 3 2 4 5 3 1 6 7 switch(config)#
This example shows the class-map configuration:
switch(config)# show class-map Type qos class-maps =================== class-map type qos match-all cqos1 match cos 1 class-map type qos match-all cqos6 match cos 6 class-map type qos match-any class-default match any Type queuing class-maps ======================= class-map type queuing cqu1 match qos-group 1 class-map type queuing cqu6 match qos-group 6 class-map type queuing class-default match qos-group 0 Type network-qos class-maps ============================== class-map type network-qos cnq1 match qos-group 1 class-map type network-qos cnq6 match qos-group 6 class-map type network-qos class-default match qos-group 0 switch(config)#
This example shows the policy-map configuration:
switch(config)# show policy-map Type qos policy-maps ==================== policy-map type qos pqos class type qos cqos1 set qos-group 1 class type qos cqos6 set qos-group 6 class type qos class-default set qos-group 0 policy-map type qos default-in-policy class type qos class-default set qos-group 0 Type queuing policy-maps ======================== policy-map type queuing pqu class type queuing cqu1 bandwidth percent 10 class type queuing cqu6 bandwidth percent 20 class type queuing class-default bandwidth percent 70 policy-map type queuing default-out-policy class type queuing class-default bandwidth percent 100 Type network-qos policy-maps =============================== policy-map type network-qos pnqos class type network-qos cnq1 mtu 1500 set cos 4 class type network-qos cnq6 mtu 1500 set cos 5 congestion-control random-detect ecn class type network-qos class-default mtu 9216 policy-map type network-qos default-nq-policy class type network-qos class-default mtu 1500 switch(config)#
This example shows all active policy maps in the system:
switch(config)# show policy-map system Type network-qos policy-maps =============================== policy-map type network-qos pnqos class type network-qos cnq1 match qos-group 1 mtu 1500 set cos 4 class type network-qos cnq6 match qos-group 6 mtu 1500 set cos 5 congestion-control random-detect ecn class type network-qos class-default match qos-group 0 mtu 9216 Service-policy (qos) input: pqos policy statistics status: disabled Class-map (qos): cqos1 (match-all) Match: cos 1 set qos-group 1 Class-map (qos): cqos6 (match-all) Match: cos 6 set qos-group 6 Class-map (qos): class-default (match-any) Match: any set qos-group 0 Service-policy (queuing) output: pqu policy statistics status: disabled Class-map (queuing): cqu1 (match-any) Match: qos-group 1 bandwidth percent 10 Class-map (queuing): cqu6 (match-any) Match: qos-group 6 bandwidth percent 20 Class-map (queuing): class-default (match-any) Match: qos-group 0 bandwidth percent 70 switch(config)#
This example shows the service policy maps configured on the interfaces:
switch(config)# show policy-map interface ethernet 1/1 Global statistics status : disabled Ethernet1/1 Service-policy (qos) input: pqos policy statistics status: disabled Class-map (qos): cqos1 (match-all) Match: cos 1 set qos-group 1 Class-map (qos): cqos6 (match-all) Match: cos 6 set qos-group 6 Class-map (qos): class-default (match-any) Match: any set qos-group 0 Service-policy (queuing) output: pqu policy statistics status: disabled Class-map (queuing): cqu1 (match-any) Match: qos-group 1 bandwidth percent 10 Class-map (queuing): cqu6 (match-any) Match: qos-group 6 bandwidth percent 20 Class-map (queuing): class-default (match-any) Match: qos-group 0 bandwidth percent 70 switch(config)#
This example shows the queuing information for a specific interface:
switch(config)# show queuing interface ethernet 1/1 Ethernet1/1 queuing information: TX Queuing qos-group sched-type oper-bandwidth 0 WRR 70 1 WRR 10 6 WRR 20 RX Queuing qos-group 0 HW MTU: 1500 (1500 configured) drop-type: drop, xon: 0, xoff: 0 Statistics: Ucast pkts sent over the port : 0 Ucast bytes sent over the port : 0 Mcast pkts sent over the port : 0 Mcast bytes sent over the port : 0 Ucast pkts dropped : 0 Ucast bytes dropped : 0 Mcast pkts dropped : 0 Mcast bytes dropped : 0 qos-group 1 HW MTU: 1500 (1500 configured) drop-type: drop, xon: 0, xoff: 0 Statistics: Ucast pkts sent over the port : 0 Ucast bytes sent over the port : 0 Mcast pkts sent over the port : 0 Mcast bytes sent over the port : 0 Ucast pkts dropped : 0 Ucast bytes dropped : 0 Mcast pkts dropped : 0 Mcast bytes dropped : 0 qos-group 6 HW MTU: 1500 (1500 configured) drop-type: drop, xon: 0, xoff: 0 Statistics: Ucast pkts sent over the port : 0 Ucast bytes sent over the port : 0 Mcast pkts sent over the port : 0 Mcast bytes sent over the port : 0 Ucast pkts dropped : 0 Ucast bytes dropped : 0 Mcast pkts dropped : 0 Mcast bytes dropped : 0 switch(config)#
The Cisco Nexus 3000 series has a 9MB buffer memory which is divided in to dedicated per port and dynamic shared memory. Each front-panel port has 8 unicast and 4 multicast queues in egress.
In the scenario of burst or congestion, each egress port consumes buffers from the dynamic shared memory.
Beginning with Cisco NX-OS Release 5.0(3)U2(1), you can display real time status of the shared buffer on a per port basis. All counters are displayed in terms of the number of cells. Each cell is 208 bytes in size. You can also display the global level buffer consumption in terms of consumption and available number of cells.
switch(config)# show hardware internal buffer info pkt-stats |-----------------------------------------------------------------------------------------| Total Instant Usage 7588 Remaining Instant Usage 38492 Max Cell Usage 7945 Switch Cell Count 46080 |-----------------------------------------------------------------------------------------| |-----------------------------------------------------------------------------------------| | Instant Buffer utilization per queue per port | | Each line displays the number of cells utilized for a given port for each QoS queue | | One cell represents approximately 208 bytes | |---------+---------+---------+---------+---------+---------+--------+---------+---------+| |Port Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 | |---------+---------+---------+---------+---------+---------+--------+---------+---------+| [ 6] UC-> 0 0 0 0 0 0 0 0 MC-> 4 0 0 0 [ 9] UC-> 0 0 0 0 0 0 0 0 MC-> 3807 0 0 0 [13] UC-> 0 0 0 0 0 0 0 0 MC-> 4 0 0 0 [19] UC-> 0 0 0 0 0 0 0 0 MC-> 3802 0 0 0
Usage information:
UC and MC represent the 8 unicast (Q1-Q8) and 4 multicast (Q1-Q4) instant cell usage. The example above shows the multicast queue Q1 is consuming 3807 cells instantaneously on port 9.
switch# clear counters buffers Max Cell Usage has been reset successfully
switch# hardware profile buffer info port-threshold front-port 1 threshold 10 Port threshold changed successfully
switch(config)# sh hardware internal buffer info pkt-stats port-log 02-27-2012 04:10:36.63345 Port 9 buffer threshold 3685 exceeded 810[3%] 02-27-2012 04:10:36.63764 Port 17 buffer threshold 3684 exceeded 2430[9%] 02-27-2012 04:10:36.65436 Port 63 buffer threshold 3681 exceeded 270[1%]