Automatic QoS 327
Automatic QoS
Auto-QoS facilitates the QoS configuration process for the Catalyst 6500. At the time of
writing, Auto-QoS is available with CatOS Software Release 7.5. Auto-QoS assists the
administrator in configuring classification, congestion management, mapping, and
congestion avoidance. The Auto-QoS feature on the Catalyst 6500 is divided into two
components. Global Auto-QoS provides recommended QoS parameters on a switch-wide
basis, whereas port-specific Auto-QoS configures parameters on a per-interface basis. With
CatOS Release 7.5, Auto-QoS commands are specifically focused on voice-related appli-
cations. However, future software releases will provide additional functionality and
capabilities.
NOTE At the time of writing, Auto-QoS is not available in Cisco IOS for the Catalyst 6500.
However, there are plans to integrate the feature in future Cisco IOS releases.
Global Auto-QoS
The global Auto-QoS command focuses on QoS parameters affecting the entire switch. To
enable global Auto-QoS, enter the following command in enable mode on the supervisor:
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When you enter the preceding command, any QoS commands previously configured are
modified. Therefore, you should enable any Auto-QoS commands prior to manually
Example 8-44 Configuring WRED Transmit Queue Thresholds in Native Mode
native(config-if)# wrr-queue random-detect min-threshold 1 75
WRED_threshold configured on all 48 ports on slot 3.
native(config-if)# wrr-queue random-detect min-threshold 2 75
WRED_threshold configured on all 48 ports on slot 3.
native(config-if)# wrr-queue random-detect min-threshold 3 80
WRED_threshold configured on all 48 ports on slot 3.
native# show queueing interface fastEthernet 3/1
Interface FastEthernet3/1 queueing strategy: Weighted Round-Robin
Port QoS is enabled
Trust state: trust IP Precedence
Default COS is 0
Transmit queues [type = 1p3q1t]:
(text omitted)
queue random-detect-min-thresholds
----------------------------------
1 75[1]
2 75[1]
3 80[1]
328 Chapter 8: QoS Support on the Catalyst 6500
altering the switch QoS properties. set qos autoqos first enables QoS on the switch, if it is
not already enabled. The global Auto-QoS command does not alter any default QoS config-
urations applied at the port level. Because congestion management, congestion avoidance,
and CoS-to-queue mappings depend on port types rather than specific ports, commands
related to these mechanisms are incorporated into the global Auto-QoS command. Refer to
Table 8-2 for a detailed list of the various modules and the corresponding port types, and
review the section “Catalyst Feature Overview” in Chapter 3, which provides additional
information on port type nomenclature. Tables 8-21 and 8-22 list the resulting commands
executed when configuring global Auto-QoS.
*Command is enabled on the switch if it was not previously enabled.
**All normal and excess rate policed DSCP map values are configured for default values. The exception is DSCP
26 and DSCP 46.
Table 8-21 Added Global Auto-QoS Configuration Commands
* set qos enable
set qos policy-source local
set qos acl default-action ip dscp 0
set qos ipprec-dscp-map 0 10 18 24 34 46 48 56
set qos cos-dscp-map 0 10 18 24 34 46 48 56
set qos dscp-cos-map 0-7:0 8-15:1 16-23:2 24-31:3 32-39:4 40-47:5 48-55:6 56-63:7
** set qos policed-dscp-map 26:0
** set qos policed-dscp-map 46:0
Table 8-22 Added Global Auto-QoS Port Type Configuration Commands
2q2t/1q4t
set qos map 2q2t tx queue 2 2 cos 5,6,7
set qos map 2q2t tx queue 2 1 cos 1,2,3,4
set qos map 2q2t tx queue 1 1 cos 0
set qos drop-threshold 2q2t tx queue 1 100 100
set qos drop-threshold 2q2t tx queue 2 80 100
set qos drop-threshold 1q4t rx queue 1 50 60 80 100
set qos txq-ratio 2q2t 80 20
set qos wrr 2q2t 100 255
1p3q1t/1p1q0t
set qos map 1p3q1t tx 1 1 cos 0
set qos map 1p3q1t tx 2 1 cos 1,2
set qos map 1p3q1t tx 3 1 cos 3,4
Automatic QoS 329
set qos map 1p3q1t tx 3 0 cos 6,7
set qos map 1p3q1t tx 4 cos 5
set qos wrr 1p3q1t 20 100 200
set qos wred 1p3q1t queue 1 70:100
set qos wred 1p3q1t queue 2 70:100
set qos wred 1p3q1t queue 3 70:90
set qos map 1p1q0t rx 1 cos 0,1,2,3,4
set qos map 1p1q0t rx 2 cos 5,6,7
set qos rxq-ratio 1p1q0t 80 20
1p2q2t/1p1q4t
set qos map 1p2q2t tx 1 2 cos 0
set qos map 1p2q2t tx 2 1 cos 1,2,3,4
set qos map 1p2q2t tx 2 2 cos 6,7
set qos map 1p2q2t tx 3 cos 5
set qos txq-ratio 1p2q2t 75 15 15
set qos wrr 1p2q2t 50 255
set qos wred 1p2q2t queue 1 1 40:70
set qos wred 1p2q2t queue 1 2 70:100
set qos wred 1p2q2t queue 2 1 40:70
set qos wred 1p2q2t queue 2 2 70:100
set qos map 1p1q4t rx 1 1 cos 0
set qos map 1p1q4t rx 1 3 cos 1,2,3,4
set qos map 1p1q4t rx 1 4 cos 6,7
set qos map 1p1q4t rx 2 cos 5
set qos rxq-ratio 1p1q4t 50 255
set qos drop-threshold 1p1q4t rx queue 1 50 60 80 100
1p2q1t/1p1q8t
set qos map 1p2q1t tx 1 1 cos 0
set qos map 1p2q1t tx 2 1 cos 1,2,3,4
set qos map 1p2q1t tx 2 cos 6,7
set qos map 1p2q1t tx 3 cos 5
Table 8-22 Added Global Auto-QoS Port Type Configuration Commands (Continued)
continues
330 Chapter 8: QoS Support on the Catalyst 6500
Port-Specific Auto-QoS
The port-specific Auto-QoS functions define, in one of two ways, the classification method
used for traffic ingress to a specific port. One way involves specifying the type of device
attached to the port, either a Cisco IP Phone or Cisco IP Softphone. The other method
requires specifying the trust state for a particular port, either trust DSCP or trust CoS.
Configuring port-specific Auto-QoS also assigns extended trust capabilities and CoS
assignments to attached IP Phones using Cisco Discovery Protocol (CDP) version 2. If
CDP version 2 is not enabled, the information cannot be communicated to an attached
Cisco IP Phone. Refer to the section “Voice VLANs and Extended Trust” in Chapter 2 for
additional information on CDP and extended port-based QoS capabilities. A PFC is a
prerequisite for using either the trust DSCP or IP Softphone Auto-QoS option. To configure
port-specific Auto-QoS, use one of the following commands:
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The “Classification and Marking” section within this chapter discusses trust and internal
DSCP in further detail. The trust dscp and trust cos classification keywords are used to
classify all traffic based on arriving DSCP or CoS values. You can use the cos keyword for
trusted uplink ports attached to devices capable of only modifying the trunk header of an
Ethernet frame. This ensures previously assigned CoS values are honored at the arriving
switch port, and subsequently mapped to a corresponding internal DSCP value. You can use
the dscp keyword for uplink ports attached to devices capable of altering the DSCP field in
the IP header. This capability is relevant, for instance, when connecting to a 3550, another
set qos txq-ratio 1p2q1t 75 15 15
set qos wrr 1p2q1t 50 255
set qos wred 1p2q1t queue 1 70:100
set qos wred 1p2q1t queue 2 70:100
set qos map 1p1q8t rx 1 1 cos 0
set qos map 1p1q8t rx 1 5 cos 1,2
set qos map 1p1q8t rx 1 8 cos 3,4
set qos map 1p1q8t rx 2 cos 5,6,7
set qos wred 1p1q8t queue 1 1 40:70
set qos wred 1p1q8t queue 1 5 60:90
set qos wred 1p1q8t queue 1 8 70:100
set qos rxq-ratio 1p1q8t 80 20
Table 8-22 Added Global Auto-QoS Port Type Configuration Commands (Continued)
Automatic QoS 331
6500, or even a router. A PFC is required to use the dscp keyword. Table 8-21 depicts the
CoS-to-DSCP and IP precedence-to-DSCP mapping values if the global Auto-QoS
command is executed; Table 8-12 shows the default assigned mapping values.
The voip ciscoipphone and voip ciscosoftphone keywords simplify the process of config-
uring voice-specific QoS on a port. The ciscoipphone option configures the ingress port to
trust the control and voice-bearer traffic received from an IP Phone. By default, this traffic
is marked by the phone with CoS 3 and CoS 5, respectively. As mentioned previously, if
CDP is enabled and the port terminates into a Cisco IP Phone, additional QoS capabilities
are extended to support devices attached to a switchport on the phone. For additional infor-
mation regarding the Cisco IP Phone, refer to the section “The Cisco IP Phone” in Chapter
2. The ciscosoftphone option configures an ingress port to trust voice traffic generated by
the Cisco Softphone application. The Softphone application properly marks the control and
voice traffic within the IP header. As a result, ACLs trusting the ingress DSCP values are
configured for the port (and, based on worst-case performance parameters, policers are
configured to regulate control and voice traffic generated by the application). A PFC is
required for configuring the ciscosoftphone keyword.
As discussed in the “Trust” section within this chapter, the WS-X6224/6248 and WS-
X6324/6348 have certain hardware limitations that prevent them from supporting certain
trust states on a port. As a result, additional intelligence has been added to the port-based
Auto-QoS command to account for this limitation. For 1q4t/2q2t port types, when the trust
cos, trust dscp, or voip ciscoipphone keywords are used, additional commands and ACLs
are configured to support the configured feature. When specifying trust cos or voip
ciscoipphone, the following additional commands are added for the port configuration:
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When specifying the trust dscp keyword, the following commands are added to complete
the port configuration:
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NOTE The WS-X6148 module is capable of supporting trust-cos, trust-dscp, and trust-ipprec.
However, this capabilitiy is integrated in 6.4, and was not included in CatOS Release 7.5.
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