Configuring Quality of Service

Note For complete syntax and usage information for the commands used in this chapter, refer to the Command Reference publication for your switch.

This chapter consists of these sections:

Typically, networks operate on a best-effort delivery basis, which means that all traffic has equal priority and an equal chance of being delivered in a timely manner. When congestion occurs, all traffic has an equal chance of being dropped.

QoS selects network traffic, prioritizes it according to its relative importance, and provides priority-indexed treatment through congestion avoidance techniques. Implementing QoS in your network makes network performance more predictable and bandwidth utilization more effective.

QoS classifies traffic by assigning priority-indexed IEEE 802.1p class of service (CoS) values to frames at supported ingress ports. On the Catalyst 5000 family switches, for IPv4 traffic destined for a router, QoS can classify packets that match an access-control entry (ACE) by setting the IP precedence bits (in the IP header) and CoS value in the frame header.

QoS implements scheduling on supported egress ports with transmit queue drop thresholds and multiple transmit queues that use the IEEE 802.1p CoS values to give preference to higher-priority traffic. Figure 15-1 shows how QoS affects the traffic flow through a Catalyst 5000 family switch.

Note Use the show port capabilities command to determine if ports on a specific module support QoS as shown in Figure 15-1.

Figure 15-1: Traffic Flow Through the Switch with QoS Enabled---Catalyst 5000 Family Switches

Figure 15-2 shows how QoS affects the traffic flow through a Catalyst 4000 family or 2948G switch.

Figure 15-2: Traffic Flow Through the Switch with QoS Enabled---Catalyst 4000 Family and 2948G Switches

QoS Terminology

The following QoS terminology is used in this chapter:

QoS uses these labels to prioritize traffic:
- Layer 2 class of service (CoS) values ---Layer 2 Inter-Switch Link (ISL) frame headers have a 1-byte User field that carries an IEEE 802.1p CoS value in the three least significant bits. Layer 2 IEEE 802.1Q frame headers have a 2-byte Tag Control Information field that carries the CoS value in the three most significant bits (the User Priority bits). Other frame types cannot carry CoS values. CoS values range between zero (low priority) and seven (high priority).
- Layer 3 IP precedence values---The IP version 4 specification defines the three most significant bits of the 1-byte Type of Service (ToS) field as IP precedence, which is used to indicate priority. IP precedence values range between zero (low priority) and seven (high priority).
Classification is the selection of traffic to be marked.
Marking is the application of QoS labels to traffic.
Scheduling is the assignment of traffic to a queue. QoS assigns traffic based on CoS values.
Congestion avoidance is the process by which QoS reserves ingress and egress port capacity for traffic with high-priority CoS values. QoS implements congestion avoidance with CoS value-based drop thresholds and transmit queues. A drop threshold is the percentage of buffer utilization at which traffic with a specified CoS value is dropped, leaving the buffer available for traffic with higher-priority CoS values. A transmit queue is a queue on the egress port where outgoing frames are stored before transmission. With multiple transmit queues, traffic with higher-priority CoS values can be placed in a reserved transmit queue.
Policing is the process by which the switch limits the bandwidth consumed by a flow of traffic. Policing can mark or drop traffic.

Understanding Classification and Marking

These sections describe the three supported methods of classification and marking:

Understanding Classification and Marking at the Ingress Port

ISL or 802.1Q frames are not classified or marked at the ingress port. The existing CoS value is honored.

When an ISL frame enters the switch through a supported ingress port, QoS accepts the three least significant bits in the User field as the CoS value.
When an 802.1Q frame enters the switch through a supported ingress port, QoS accepts the User Priority bits as the CoS value.

On the Catalyst 5000 family switches, QoS classifies and marks all other frame types that enter the switch through a supported ingress port with the configured CoS value of the port (the default is zero). On the Catalyst 4000 family and 2948G switches, QoS classifies and marks all other frame types that enter the switch with the default CoS value configured for the entire switch. You cannot mark traffic on a per-port basis.

Note The Catalyst 4000 family and 2948G switches only support frame classification and marking on unclassified frames entering the switch. Destination-based and Layer 3 ACE-based classification is not supported.

Understanding Classification and Marking Based on Destination

On the Catalyst 5000 family switches, QoS can rewrite the CoS value with a configurable value in frames destined for selected destination host Media Access Control (MAC) address and VLAN pairs (see the "Mapping a CoS Value to a Host Destination MAC Address/VLAN Pair" section). Destination-based marking overwrites any CoS value previously written, including port-based CoS values.

Understanding Classification and Marking Based on an ACE

On the Catalyst 5000 family switches, for IPv4 traffic destined for a router, QoS can perform classification of traffic that matches the parameters in an ACE under the following conditions:

If Multilayer Switching (MLS) is disabled, QoS can perform ACE-based classification of all traffic destined for a router. Specify router MAC addresses using the set qos router-mac command (see "Entering the MAC Address of a Router" section).
If MLS is enabled:
- QoS can perform ACE-based classification of all traffic destined for a router other than the Multilayer Switching Route Processor (MLS-RP). Specify router MAC addresses using the set qos router-mac command.
- For traffic destined for the MLS-RP, QoS can perform ACE-based classification only for traffic that is switched using MLS. ACE-based classification is performed at the switch egress port as the flow is being multilayer switched. QoS cannot perform ACE-based classification on traffic that the MLS-RP routes off the switch. QoS learns the address of the MLS-RP automatically when MLS is configured on the switch.
Use the show mls entry qos command to display information about the Layer 3-switched traffic on which QoS has performed ACE-based classification. QoS might take up to 1 second to start ACE-based classification of Layer 3-switched traffic.

If ACE-based classification occurs, QoS sets the IP precedence bits in the IP header to match the CoS value. ACE-based marking overwrites any CoS value previously written, including port-based and destination-based CoS values.

These parameters can be specified in an ACE:

Layer 3 destination IP address and netmask
Layer 3 source IP address and netmask
Layer 4 protocol (tcp, udp, or any)
Layer 4 destination port number (can be a wildcard)
Layer 4 source port number (can be a wildcard)

For information on configuring ACEs, see the "Creating an Access Control Entry" section.

Understanding Scheduling

On the Catalyst 5000 family switches, there is one non-user-configurable transmit queue and four user-configurable transmit queue drop thresholds for each port. Ports of this type are specified using the 1q4t keyword in QoS-related commands.

QoS uses the transmit queue drop thresholds to schedule transmission of network traffic from the switch through supported egress ports. By default, the four transmit queue drop thresholds function as follows:

Threshold 1---Frames with CoS 0 or 1 are dropped when the transmit queue buffer is 30 percent full.
Threshold 2---Frames with CoS 2 or 3 are dropped when the transmit queue buffer is 50 percent full.
Threshold 3---Frames with CoS 4 or 5 are dropped when the transmit queue buffer is 80 percent full.
Threshold 4---Frames with CoS 6 or 7 are dropped when the transmit queue buffer is 100 percent full.

Note To configure the transmit queue drop threshold percentages on the Catalyst 5000 family switches, see the "Configuring Transmit Queue Drop Thresholds" section. To configure the CoS values mapped to each threshold on the Catalyst 5000 family switches, see the "Mapping CoS Values to Transmit Queues and Drop Thresholds" section. All 1q4t ports in the switch use the same drop threshold configuration.

On the Catalyst 4000 family and 2948G switches, there are two user-configurable transmit queues and a single non-user-configurable transmit queue drop threshold for each port. Ports of this type are specified using the 2q1t keyword in QoS-related commands.

QoS uses the transmit queues to schedule transmission of network traffic from the switch through egress ports. By default, all traffic is assigned to queue 1 and threshold 1 when QoS is enabled. All traffic destined for a transmit queue, regardless of classification, is subject to tail drop when the queue is full (that is, frames at the end of the queue are dropped).

Caution On the Catalyst 4000 family and 2948G switches, when QoS is disabled, unicast traffic is assigned to queue 1 and broadcast, multicast, and unknown traffic is assigned to queue 2. If you enable QoS but do not modify the CoS-to-transmit queue mappings, switch performance could be affected because all traffic is assigned to queue 1. If you enable QoS, we recommend that you modify the CoS-to-transmit queue mappings.

Note To configure the CoS values mapped to each transmit queue on the Catalyst 4000 family and 2948G switches, see the "Mapping CoS Values to Transmit Queues and Drop Thresholds" section.

Hardware and Software Requirements

QoS requires these software and hardware versions:

Supervisor engine software:
- Catalyst 5000 family switches---Software release 5.1 or later
- Catalyst 4000 family and 2948G switches---Software release 5.2 or later

On Catalyst 5000 family switches, the following hardware is required:

Supervisor Engine II G or III G; or Supervisor Engine III or III F with a NetFlow Feature Card II (NFFC II)
One or more Ethernet switching modules that support QoS (QoS requires that traffic is received and transmitted on supported ports):
- 4-port 10/100BaseTX Fast EtherChannel uplink module (WS-U5537-FETX)
- 4-port 100BaseFX MMF MT-RJ Fast EtherChannel uplink module (WS-U5538-FEFX-MMF)
- 24-port 10/100BaseTX Fast Ethernet RJ-45 (WS-X5234-RJ45)
- 24-port 100BaseFX Fast Ethernet MT-RJ (WS-X5236-FX-MT)
- 36-port 10/100BaseTX Fast Ethernet Telco (WS-X5239-RJ21)

Use the show port capabilities command to determine the specific QoS support for a module.

QoS Default Configuration

Table 15-1 shows the QoS default configuration.

Table 15-1: QoS Default Configuration

Feature Default Value

QoS global enable state

Disabled

Port CoS value (Catalyst 5000 family)

0

Switch CoS value (Catalyst 4000 family and 2948G)

0

Transmit queue drop threshold percentages

Catalyst 5000 family:

Threshold 1: 30%

Threshold 2: 50%

Threshold 3: 80%

Threshold 4: 100%

Catalyst 4000 family and 2948G:

Threshold 1: 100%¹

CoS value-to-drop threshold mapping

Catalyst 5000 family:

Transmit queue drop threshold 1: CoS 0-1

Transmit queue drop threshold 2: CoS 2-3

Transmit queue drop threshold 3: CoS 4-5

Transmit queue drop threshold 4: CoS 6-7

Catalyst 4000 family and 2948G:

Transmit queue drop threshold 1: CoS 0-7¹

CoS value-to-transmit queue mapping

Catalyst 5000 family:

Transmit queue 1: CoS 0-7¹

Catalyst 4000 family and 2948G:

Transmit queue 1: CoS 0-7

Transmit queue 2: None configured

¹ Non-user-configurable

Feature	Default Value
QoS global enable state	Disabled
Port CoS value (Catalyst 5000 family)	0
Switch CoS value (Catalyst 4000 family and 2948G)	0
Transmit queue drop threshold percentages	Catalyst 5000 family: Threshold 1: 30% Threshold 2: 50% Threshold 3: 80% Threshold 4: 100% Catalyst 4000 family and 2948G: Threshold 1: 100%¹
CoS value-to-drop threshold mapping	Catalyst 5000 family: Transmit queue drop threshold 1: CoS 0-1 Transmit queue drop threshold 2: CoS 2-3 Transmit queue drop threshold 3: CoS 4-5 Transmit queue drop threshold 4: CoS 6-7 Catalyst 4000 family and 2948G: Transmit queue drop threshold 1: CoS 0-7¹
CoS value-to-transmit queue mapping	Catalyst 5000 family: Transmit queue 1: CoS 0-7¹ Catalyst 4000 family and 2948G: Transmit queue 1: CoS 0-7 Transmit queue 2: None configured

Configuring QoS

These sections describe how to configure QoS:

Note Because entering some QoS commands disables and then reenables ports (which can cause spanning-tree topology changes), enter QoS commands only when necessary.

Enabling QoS Globally

To enable QoS globally on the switch, perform this task in privileged mode:

Task Command

Enable QoS on the switch.

set qos enable

Task	Command
Enable QoS on the switch.	set qos enable

This example shows how to enable QoS:

Console> (enable) set qos enable
QoS is enabled.
Console> (enable)

Configuring the Default CoS Value for the Switch

On the Catalyst 4000 family and 2948G switches, QoS assigns unclassified frames received on any port on the switch the CoS value configured for the switch. The default CoS value is zero.

Note You cannot configure a switch-default CoS value on the Catalyst 5000 family switches.

To set the default CoS value for a Catalyst 4000 family or 2948G switch, perform this task in privileged mode:

Task Command

Step 1 Set the CoS value for the switch.

set qos defaultcos cos-value

Step 2 Verify the CoS value of the switch.

show qos info [runtime | config]

Task	Command
Step 1 Set the CoS value for the switch.	set qos defaultcos cos-value
Step 2 Verify the CoS value of the switch.	show qos info [runtime \| config]

This example shows how to set CoS equal to 7 in all unclassified frames received on the switch and verify the configuration:

Console> (enable) set qos defaultcos 7
qos defaultcos set to 7
Console> (enable)

Configuring the CoS Value for a Port

On the Catalyst 5000 family switches, QoS assigns to unclassified frames received through a supported port the CoS value configured for that port. The default CoS value is zero.

Note You cannot configure port-specific CoS values on the Catalyst 4000 family and 2948G switches.

To set the CoS value for a port, perform this task in privileged mode:

Task Command

Step 1 Set the CoS value for a port.

set port qos mod_num/port_num cos cos-value

Step 2 Verify the CoS value of the port.

show port qos mod_num/port_num

Task	Command
Step 1 Set the CoS value for a port.	set port qos mod_num/port_num cos cos-value
Step 2 Verify the CoS value of the port.	show port qos mod_num/port_num

This example shows how to set CoS equal to 7 in all unclassified frames received through port 8/1 and verify the configuration:

Console> (enable) set port qos 8/1 cos 7 
Port 8/1 qos cos set to 7
Console> (enable) show port qos 8/1 
QoS is enabled on 8/1
Port 8/1 has 1 transmit queue with 4 drop thresholds (1q4t).
QoS setting in NVRAM:
Default CoS = 7    
Run time setting of QoS:
Default CoS = 7 
Console> (enable)

Reverting to the Default Switch CoS Value

On the Catalyst 4000 family and 2948G switches, to revert to the default switch CoS value, perform this task in privileged mode:

Task Command

Step 1 Revert to the default CoS value for the switch.

clear qos defaultcos

Step 2 Verify that the default CoS value was restored.

show qos info [runtime | config]

Task	Command
Step 1 Revert to the default CoS value for the switch.	clear qos defaultcos
Step 2 Verify that the default CoS value was restored.	show qos info [runtime \| config]

This example shows how to revert to the default CoS value for port 8/1 and verify the configuration:

Console> (enable) clear qos defaultcos
qos defaultcos setting cleared.
Console> (enable)

Reverting to the Default Port CoS Value

On the Catalyst 5000 family switches, to revert to the default CoS value for a port, perform this task in privileged mode:

Task Command

Step 1 Revert to the default CoS value for a port.

clear port qos mod_num/port_num cos

Step 2 Verify that the default CoS value was restored.

show port qos mod_num/port_num

Task	Command
Step 1 Revert to the default CoS value for a port.	clear port qos mod_num/port_num cos
Step 2 Verify that the default CoS value was restored.	show port qos mod_num/port_num

This example shows how to revert to the default CoS value for port 8/1 and verify the configuration:

Console> (enable) clear port qos 8/1 cos
Port 8/1 qos cos setting cleared.
Console> (enable) show port qos 8/1 
QoS is enabled on 8/1
Port 8/1 has 1 transmit queue with 4 drop thresholds (1q4t).
QoS setting in NVRAM:
Default CoS = 0 
Run time setting of QoS:
Default CoS = 0 
Console> (enable)

Mapping a CoS Value to a Host Destination MAC Address/VLAN Pair

Note You cannot map MAC address/VLAN pairs to CoS values on the Catalyst 4000 family and 2948G switches.

To assign a CoS value to all frames destined for a particular host destination MAC address and VLAN number pair, perform this task in privileged mode:

Task Command

Step 1 Assign a CoS value to a host destination MAC address/VLAN number pair.

set qos mac-cos dest_MAC_addr VLAN cos_value

Step 2 Verify the assigned CoS value.

show qos mac-cos dest_MAC_addr [VLAN]

show qos mac-cos all

Task	Command
Step 1 Assign a CoS value to a host destination MAC address/VLAN number pair.	set qos mac-cos dest_MAC_addr VLAN cos_value
Step 2 Verify the assigned CoS value.	show qos mac-cos dest_MAC_addr [VLAN] show qos mac-cos all

This example shows how to assign CoS 2 to a destination MAC address and VLAN number pair and verify the configuration:

Console> (enable) set qos mac-cos 00-40-0b-30-03-48 525 2
CoS 2 is assigned to 00-40-0b-30-03-48 vlan 525.
Console> (enable) show qos mac-cos 00-40-0b-30-03-48
VLAN  Dest MAC            CoS
----  ------------------  ---
525   00-40-0b-30-03-48   2 
Console> (enable)

Creating an Access Control Entry

Use the set qos ip-filter command to create access control entries (ACEs) with Layer 3 values or with both Layer 3 and 4 values.

Note You cannot configure ACEs on the Catalyst 4000 family and 2948G switches.

The dest_addr/wildcardmask parameter is the destination IP address and netmask. The src_addr/wildcardmask parameter is the source IP address and netmask. The cos (CoS) parameter range is 0-7. The address and wildcard mask (use one bits in where you want wildcards) can specify a network, subnet, or host address.

Frames are compared to the access control entries sequentially. QoS uses the first match found. By default, ACE entries are added to the end of the access control list. Use the optional before ACE# keyword and parameter to position an entry within the list (use the show qos ip command to display the access control list).

The dst_port parameter is the Layer 4 destination port number. The src_port parameter is the Layer 4 source port number. You can use zero as a wildcard for either or both port numbers.

To create an ACE, perform this task in privileged mode:

Task Command

Step 1 Create an ACE.

set qos ip-filter cos dest_addr/wildcardmask src_addr/wildcardmask [before ACE#]

set qos ip-filter cos dest_addr/wildcardmask src_addr/wildcardmask {tcp | udp | any} dst_port src_port [before ACE#>]

Step 2 Verify the entry.

show qos ip

Task	Command
Step 1 Create an ACE.	set qos ip-filter cos dest_addr/wildcardmask src_addr/wildcardmask [before ACE#] set qos ip-filter cos dest_addr/wildcardmask src_addr/wildcardmask {tcp \| udp \| any} dst_port src_port [before ACE#>]
Step 2 Verify the entry.	show qos ip

This example shows how to create ACEs and an ACE within the list and verify the configuration:

Console> (enable) set qos ip 7 100.100.1.1/0.0.0.255 200.200.1.1/0.0.0.255 
qos ip-filter is set successfully.
Console> (enable) show qos ip 
There are 1 IP filter(s).
ACE# Dest IP/Mask                     Src IP/Mask                    
---- -------------------------------- --------------------------------
   1 100.100.1.1/0.0.0.255            200.200.1.1/0.0.0.255       
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     both     0        0        7  
Console> (enable) set qos ip 4 120.100.1.1/0.0.0.255 210.210.1.1/0.0.0.255 tcp 23 47 
qos ip-filter is set successfully.
Console> (enable) sh qos ip 
There are 2 IP filter(s).
ACE# Dest IP/Mask                     Src IP/Mask                    
---- -------------------------------- --------------------------------
   1 100.100.1.1/0.0.0.255            200.200.1.1/0.0.0.255       
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     both     0        0        7  
 
   2 120.100.1.1/0.0.0.255            210.210.1.1/0.0.0.255       
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     tcp      23       47       4  
 
Console> (enable) set qos ip-filter 1 20.20.20.1/255.0.0.0 30.30.1.1/255.0.0.0 before 1
qos ip-filter is set successfully.
Console> (enable) sh qos ip 
There are 3 IP filter(s).
ACE# Dest IP/Mask                     Src IP/Mask                    
---- -------------------------------- --------------------------------
   1 20.20.20.1/255.0.0.0             30.30.1.1/255.0.0.0             
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     both     0        0        1  
 
   2 100.100.1.1/0.0.0.255            200.200.1.1/0.0.0.255       
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     both     0        0        7  
 
   3 120.100.1.1/0.0.0.255           210.210.1.1/0.0.0.255       
     Protocol Dst Port Src Port CoS
     -------- -------- -------- ---
     tcp      23       47       4

Entering the MAC Address of a Router

Use this command to enter router addresses used by QoS, except for the MLS-RP.

Note You cannot specify router MAC addresses on the Catalyst 4000 family and 2948G switches.

To configure a router address, perform this task in privileged mode:

Task Command

Step 1 Configure a router for use with QoS.

set qos router-mac MAC_addr vlan

Step 2 Verify the configuration.

show qos router-mac [MAC_addr | vlan]

Task	Command
Step 1 Configure a router for use with QoS.	set qos router-mac MAC_addr vlan
Step 2 Verify the configuration.	show qos router-mac [MAC_addr \| vlan]

This example shows how to configure a router address in VLAN 2:

Console> (enable) set qos router-mac 00-40-0b-30-03-48 2
Router MAC/Vlan is set for QoS.
Console> (enable) show qos router-mac 00-40-0b-30-03-48
Number  MAC address        Vlan #
---------------------------------
     1  00-40-0b-30-03-48  2
Console> (enable)

Removing a Router Address

To remove a router or all routers from the QoS configuration, perform this task in privileged mode:

Task Command

Step 1 Remove a router or all routers from the QoS configuration.

clear qos router-mac MAC_addr vlan

clear qos router-mac all

Step 2 Verify the configuration.

show qos router-mac

Task	Command
Step 1 Remove a router or all routers from the QoS configuration.	clear qos router-mac MAC_addr vlan clear qos router-mac all
Step 2 Verify the configuration.	show qos router-mac

This example shows how to clear a router address in VLAN 2:

Console> (enable) clear qos router-mac 00-40-0b-30-03-48 2
QoS Router MAC/Vlan(s) cleared.
Console> (enable)

Configuring Transmit Queue Drop Thresholds

Use the set qos wred-threshold command to set the transmit queue drop thresholds.

Note You cannot configure transmit queue drop thresholds on the Catalyst 4000 family and 2948G switches.

The port_type is hardware-dependent. Use the show port capabilities command to determine the port_type for your hardware. The port type is defined by the number of transmit queues and the number of drop thresholds supported on the port. For example, the 1q4t port type supports one transmit queue and four drop thresholds.

The q# is the transmit queue number. The thresholds are specified as percentages, ranging from 1 to 100. A value of 10 indicates a threshold when the buffer is 10 percent full. The number of threshold percentages you can specify depends on the port_type.

To configure the transmit queue drop thresholds on all ports in the switch, perform this task in privileged mode:

Task Command

Set the transmit drop queue thresholds.

set qos wred-threshold port_type tx queue q# threshold_percentage_values

Task	Command
Set the transmit drop queue thresholds.	set qos wred-threshold port_type tx queue q# threshold_percentage_values

This example shows how to configure the transmit queue drop thresholds:

Console> (enable) set qos wred-threshold 1q4t tx queue 1 30 50 80 100
Transmit drop thresholds for queue 1 set at 30% 50% 80% 100%
Console> (enable)

Mapping CoS Values to Transmit Queues and Drop Thresholds

Use the set qos map command to associate CoS values to transmit queue drop thresholds.

The q# is the transmit queue number. The threshold# is the drop threshold number for the specified queue.

The cos_list is the list of CoS values to map to the specified transmit queue and drop threshold. On the Catalyst 4000 family and 2948G switches, CoS values must be specified in pairs (0-1, 2-3, 4-5, and 6-7).

To associate CoS values to a transmit queue and drop threshold, perform this task in privileged mode:

Task Command

Associate a CoS value to a transmit queue and drop threshold.

set qos map port_type q# threshold# cos cos_list

Task	Command
Associate a CoS value to a transmit queue and drop threshold.	set qos map port_type q# threshold# cos cos_list

This example shows how to assign the CoS values 4 through 7 to the first transmit queue and the second drop threshold for that queue on a 1q4t port (Catalyst 5000 family switches):

Console> (enable) set qos map 1q4t 1 2 cos 4-7
Qos tx priority queue and threshold mapped to cos successfully.
Console> (enable)

This example shows how to map CoS values 4 through 7 to the second transmit queue and the first drop threshold for that queue on a 2q1t port (Catalyst 4000 family and 2926G switches):

Console> (enable) set qos map 2q1t 2 1 cos 4-7
Qos tx priority queue and threshold mapped to cos successfully.
Console> (enable)

Reverting to the Default CoS-to-Transmit Queue and Drop Threshold Mapping

Use the clear qos map command to revert to the default CoS-to-transmit queue and drop threshold mappings.

The port_type is hardware-dependent. Use the show port capabilities command to determine the port_type for your hardware.

To revert to the default CoS-to-transmit queue and drop threshold mappings, perform this task in privileged mode:

Task Command

Revert to default CoS-to-transmit queue and drop threshold mappings.

clear qos map port_type

Task	Command
Revert to default CoS-to-transmit queue and drop threshold mappings.	clear qos map port_type

This example shows how to return the CoS-to-transmit queue and drop threshold mappings to the default values on 1q4t ports (Catalyst 5000 family switches):

Console> (enable) clear qos map 1q4t 
Qos map setting cleared.
Console> (enable)

This example shows how to return the CoS-to-transmit queue and drop threshold mappings to the default values on 2q1t ports (Catalyst 4000 family and 2948G switches):

Console> (enable) clear qos map 2q1t 
Qos map setting cleared.
Console> (enable)

Displaying QoS Statistics

Note The show qos statistics command is not supported on the Catalyst 4000 family and 2948G switches.

To display QoS statistics, perform this task:

Task Command

Display QoS statistics.

show qos statistics [mod_num[/port_num]]

Task	Command
Display QoS statistics.	show qos statistics [mod_num[/port_num]]

This example shows how to display QoS statistics for port 8/1:

Console> show qos statistics 8/1
On Transmit:Port 8/1 has 1 Queue(s) 4 Threshold(s)
Q #  Threshold #:Packets dropped
---  -----------------------------------------------
1    1:63551 pkts, 2:0 pkts, 3:0 pkts, 4:0 pkts
Console>

Displaying QoS Information

To display QoS information, perform one of these tasks:

Task Command

Catalyst 5000 family switches:

Display QoS information.

show qos info [runtime | config] mod_num/port_num

Display QoS information about the transmit queues.

show qos info config port_type tx

Catalyst 4000 family and 2948G switches:

Display QoS information.

show qos info [runtime | config]

Task	Command
Catalyst 5000 family switches:
Display QoS information.	show qos info [runtime \| config] mod_num/port_num
Display QoS information about the transmit queues.	show qos info config port_type tx
Catalyst 4000 family and 2948G switches:
Display QoS information.	show qos info [runtime \| config]

This example shows how to display the QoS information currently in NVRAM for port 1/1:

Console> show qos info runtime 8/1
Run time setting of QoS:
QoS is enabled
Port 8/1 has 1 transmit queue with 4 drop thresholds (1q4t).
Default CoS = 0    
Queue and Threshold Mapping:
Queue Threshold CoS            
----- --------- ---------------
1     1         0 1 
1     2         2 3 
1     3         4 5 
1     4         6 7 
Tx WRED thresholds:
Queue #  Thresholds in percentage ( in abs values )
-------  ------------------------------------------
1        14% (16380 bytes) 28% (32764 bytes) 57% (65532 bytes) 100% (131068 bytes) 
Console>

This example shows how to display the QoS information for the transmit queue:

Console> (enable) show qos info config 1q4t tx
QoS setting in NVRAM for 1q4t transmit:
QoS is enabled
Queue and Threshold Mapping:
Queue Threshold CoS            
----- --------- ---------------
1     1         0 1 
1     2         2 3 
1     3         4 5 
1     4         6 7 
Tx WRED thresholds:
Queue #  Thresholds in percentage ( in abs values )
-------  ------------------------------------------
1        14% 28% 57% 100% 
Console>

This example shows how to display the current QoS configuration information for the switch (Catalyst 4000 family and 2948G switches):

Console> show qos info config
QoS setting in NVRAM:
QoS is enabled
All ports have 2 transmit queues with 1 drop thresholds (2q1t).
Default CoS = 4    
Queue and Threshold Mapping:
Queue Threshold CoS            
----- --------- ---------------
1     1         0 1 2 3 
2     1         4 5 6 7 
Console>

Reverting to QoS Defaults

To revert to QoS defaults, perform this task in privileged mode:

Task Command

Revert to QoS defaults.

clear qos config

Task	Command
Revert to QoS defaults.	clear qos config

This example shows how to revert to QoS defaults:

Console> (enable) clear qos config
This command will disable QoS and take values back to factory default.
Do you want to continue (y/n) [n]? y
QoS config cleared.
Console> (enable)

Note Reverting to defaults disables QoS, since QoS is disabled by default.

Disabling QoS

To disable QoS, perform this task in privileged mode:

Task Command

Disable QoS on the switch.

set qos disable

Task	Command
Disable QoS on the switch.	set qos disable

This example shows how to disable QoS:

Console> (enable) set qos disable
QoS is disabled.
Console> (enable)

Table of Contents

Configuring Quality of Service