Cisco IE 4000, Software Configuration Manual

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Configuring QoS
Configuring QoS
The packets are not modified (the CoS, DSCP, and IP precedence values in the packet are not changed). Traffic is
switched in pass-through mode without any rewrites and classified as best effort without any policing.
QoS Configuration Guidelines

You can configure QoS only on physical ports.

On a port configured for QoS, all traffic received through the port is classified, policed, and marked according to the
input policy map attached to the port. On a trunk port configured for QoS, traffic in all VLANs received through the
port is classified, policed, and marked according to the policy map attached to the port. If a per-port, per-VLAN
policy map is attached, traffic on the trunk port is classified, policed, and marked for the VLANs specified in the
parent-level policy, according to the child policy map associated with each VLAN.

If you have EtherChannel ports configured on your switch, you must configure QoS classification, policing, mapping,
and queuing on the individual physical ports that comprise the EtherChannel. You must decide whether the QoS
configuration should match on all ports in the EtherChannel.

Control traffic (such as spanning-tree bridge protocol data units [BPDUs] and routing update packets) received by
the switch are subject to all ingress QoS processing.

You are likely to lose data when you change queue settings; therefore, try to make changes when traffic is at a
minimum.

When you try to attach a new policy to an interface and this brings the number of policer instances to more than
1024 minus 1 more than the number of interfaces on the switch255, you receive an error message, and the
configuration fails.

When you try to attach new policy to an interface, increasing the number of policer profiles to more than 256, you
receive an error message, and the configuration fails. A profile is a combination of commit rate, peak rate, commit
burst, and peak burst. You can attach one profile to multiple instances, but if one of these characteristics differs, the
policer is considered to have a new profile.

You can specify 256 unique VLAN classification criteria within a per-port, per-VLAN policy-map, across all ports on
the switch. Any policy attachment or change that causes this limit to be exceeded fails with a VLAN label resources
exceeded error message.

You can attach per-port and per-port, per-VLAN policy-maps across all ports on the switch until QoS ACE
classification resource limitations are reached. Any policy attachment or change that causes this limit to be exceeded
fails with a
TCAM resources exceeded error message.

When CPU protection is enabled, you can configure only 45 policers per port. Disabling CPU protection allows you
to configure up to 64 policers per port. You can enter the
show policer cpu uni-eni { drop | rate } privileged EXEC
command to see if CPU protection is enabled.

Note these limitations when you disable CPU protection:
— When CPU protection is disabled, you can configure a maximum of 63 policers per port (62 on every 4th port)
for user-defined classes, and one for class-default. Any policy attachment or change that causes this limit to be
exceeded fails with a
policer resources exceeded error message.
— When CPU protection is disabled, you can configure a maximum of 256 policers on the switch. Any policy
attachment or change that causes this limit to be exceeded fails with a
policer resources exceeded error
message.
— If you disable CPU protection and attach a policy map with more than 45 policers, and then enable CPU
protection again, and reload, 19 policers per port are again required for CPU protection. During reload, the
policers 46 and above will reach the
policer resources exceeded error condition and no policers are attached
to those classes.