Specifications

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The above diagram shows QoS processing performed by the Port ASIC for outbound traffic. Some of the processes

invoked on outbound QoS processing includes:

1. Transmit Tail Drop and WRED threshold assignments

2. CoS to Transmit Tail Drop and WRED maps

3. DSCP Rewrite

4. CoS Rewrite for ISL/802.1Q frames

Also, not shown on the diagram above, is the process of reassigning the CoS to the outbound frame using a DSCP

to CoS Map; this would occur prior to the egress port performing congestion management.

The following sections will look in more detail at the QoS configuration capabilities of the port based ASIC’s.

7.1 Enabling QoS

Before any QOS configuration can take place on the Catalyst 6500, QoS must first be enabled on the switch. This is

achieved using the following command:

Cat6500(config)# mls qos

The state of QoS on the given switch can be inspected using the following command

Cat6500# show mls qos

QoS is enabled globally

Policy marking depends on port_trust

QoS ip packet dscp rewrite disabled globally

QoS serial policing mode disabled globally

Input mode for GRE Tunnel is Pipe mode

Input mode for MPLS is Pipe mode

QoS Trust state is DSCP on the following interface:

Te1/1

Vlan or Portchannel(Multi-Earl) policies supported: Yes

Egress policies supported: Yes

QoS 10g-only mode supported: Yes [Current mode: Off]

----- Module [1] -----

QoS global counters:

Total packets: 11577766

IP shortcut packets: 11465022

Packets dropped by policing: 0

IP packets with TOS changed by policing: 6798339

IP packets with COS changed by policing: 1024715

Non-IP packets with COS changed by policing: 0

MPLS packets with EXP changed by policing: 0

----- Module [5] -----

QoS global counters: