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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Configuring Standard QoS
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Only one ACL per class map and only one match class-map configuration command per class map
are supported. The ACL can have multiple access control entries, which are commands that match
fields against the contents of the packet.
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When classifying traffic on a per-port per-VLAN basis, you must use the match-all keyword with
the class-map global configuration command. For more information, see the
on a Per-Port Per-VLAN Basis by Using Class Maps” section on page 29-41
.
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The switch has only 256 VLAN labels (a few are always used internally for defaults), which are
shared between VLAN maps and per-port per-VLAN policing. If a large number of VLANs are used
in class maps and either different ACL actions are performed on them or they have different VLAN
maps applied, the available VLAN labels might be insufficient. As a consequence, the TCAM
entries are not programmed, and the feature does not work. Use the show tcam qos tcam-id
port-labels vlan-labels privileged EXEC command to display how many VLAN labels are in use
by this QoS feature.
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It is not possible to match IP fragments against configured IP extended ACLs to enforce QoS. IP
fragments are sent as best-effort. IP fragments are denoted by fields in the IP header.
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You can match IP options against configured IP extended ACLs to enforce QoS. These packets are
sent to the CPU and processed by software. IP options are denoted by fields in the IP header.
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You can configure a policer on an ingress or egress physical port; you can configure a per-port
per-VLAN policer only on an ingress port (specifies the bandwidth limits for the traffic on a
per-VLAN basis, for a given port). You cannot police at the switch virtual interface level.
You cannot configure per-port per-VLAN policing on routed ports or on virtual (logical) interfaces.
It is supported only on an ingress port configured as a trunk or as a static-access port.
The switch does not support per-VLAN QoS or VLAN QoS policing across the entire switch.
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Use only the match ip dscp dscp-list class-map configuration command in a policy map that is
attached to an egress interface.
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You cannot classify traffic by using a port trust state (for example, mls qos trust [cos | dscp |
ip-precedence] and by using a policy map (for example, service-policy input policy-map-name) at
the same time on an interface. These commands are mutually exclusive. The last one configured
overwrites the previous configuration.
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You cannot use the service-policy interface configuration command to attach policy maps that
contain these elements to an egress interface:
–
set or trust policy-map class configuration commands. Instead, you can use the police
policy-map class configuration command to mark down (reduce) the DSCP value at the egress
interface.
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Access control list (ACL) classification.
–
Per-port per-VLAN classification.
The only match criterion in a policy map that can be attached to an egress interface is the match ip
dscp dscp-list class-map configuration command.
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You can create an aggregate policer that is shared by multiple traffic classes within the same policy
map. However, you cannot use the aggregate policer across different policy maps or interfaces.
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All ingress QoS processing actions apply to control traffic (such as spanning-tree bridge protocol
data units [BPDUs] and routing update packets) that the switch receives.