290 Chapter 8: QoS Support on the Catalyst 6500
Example 8-22 Configuring and Applying a QoS Policy in Native Mode (Continued)
Policy Map VideoConf
class Control-traffic
set ip dscp 26
After the policy map parameters have been established, you must apply the QoS policy to
the appropriate interface to complete the process. Here, the desired interface is Gigabit 5/
1, and the service-policy input {name} command is configured referencing policy map
VideoConf.
native(config)# interface gigabitEthernet 5/1
native(config-if)# service-policy input VideoConf
native# show policy-map interface gigabitEthernet 5/1
GigabitEthernet5/1
service-policy input: VideoConf
class-map: Control-traffic (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
match: access-group 110
(text omitted)
native# show mls qos ip ingress
QoS Summary [IP]: (* - shared aggregates, Mod - switch module)
Int Mod Dir Cl-map DSCP AgId Trust FlId AgForward-Pk AgPoliced-Pk
--------------------------------------------------------------------------------
Gi5/1 1 I Control-t 26 3 No 0 0 0
(text omitted)
native# show queueing interface gigabitEthernet 5/1
Interface GigabitEthernet5/1 queueing strategy: Weighted Round-Robin
Port QoS is enabled
Port is untrusted
Default COS is 2
(text omitted)
Finally, after the appropriate steps for MQC have been completed, you can verify behavior.
As demonstrated, show policy-map interface {type num} and show mls qos ip ingress
detail the policy map class information. Specifically, the outputs include the ACL refer-
enced in the class map and the DSCP value used to mark all conforming traffic. Based on
the information in Table 8-11, and the output extracted from show queueing interface
{type num}, note that the port is configured as untrusted. This implies all traffic matching
the ACL is marked with DSCP 26. Recall that set ip dscp overrides interfaces with an
untrusted port trust state. All remaining traffic is marked with the default CoS value of 2.
As mentioned previously, this configuration is possible with Cisco IOS Release
12.1(12c)E1 and later. For earlier versions, it is necessary to configure a policer to mark all
desired traffic. Policing is covered later in the chapter.
Mapping
After a frame header has been forwarded from the ingress port to the switching engine, and
the appropriate priority value has been established, the PFC determines an internal DSCP
value for the frame. This value is used to signify how a frame is handled while it traverses
the switch, and ultimately how it is scheduled upon egress. A DSCP value is applied to all
frames processed by the switching engine, regardless of traffic type. This behavior is also
independent of the operating system. However, the manner for configuring the tables is
different between Native mode and Hybrid mode. Table 8-12 shows the default mapping
values used by the 6500.