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37-36
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service
Configuring QoS on Supervisor Engines II-Plus, II+10GE, IV, V, V-10GE, 4924, 4948, and 4948-10GE
This example shows how to attach the policy map named pmap1 to Fast Ethernet interface 5/36 and to
verify the configuration:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface fastethernet 5/36
Switch(config-if)# service-policy input pmap1
Switch(config-if)# end
Switch# show policy-map interface fastethernet 5/36
FastEthernet6/1
service-policy input:p1
class-map:c1 (match-any)
238474 packets
match:access-group 100
38437 packets
police:aggr-1
Conform:383934 bytes Exceed:949888 bytes
class-map:class-default (match-any)
0 packets
match:any
0 packets
Switch#
Configuring CoS Mutation
Service providers providing Layer 2 VPNs carry double-tagged or Q-in-Q traffic with the outer tag
representing the service providers’ VLAN, and the inner tag representing the customers’ VLAN.
Differentiated levels of service can be provided inside the SP network based on the CoS present in the
outer tag.
By using CoS mutation on a dot1q tunnel port, the CoS value on the outer tag of dot1q tunneled packets
entering the provider core network can be derived from the CoS of the customer VLAN tag. This allows
providers to preserve customer QoS semantics using their network.
CoS mutation is achieved through explicit user configuration to match on specific incoming CoS values
and specifying the internal DSCP that is associated for matched packets. This internal DSCP gets
converted to CoS through DSCP-CoS mapping during exit from the switch and is the CoS value that gets
marked on the outer VLAN tag.
During the process, the CoS in inner tag is preserved and is carried across in the service providers’
network.
The following example shows how a policy map preserves customer VLAN IDs and CoS values
throughout the network:
Class Map match-any c0
Match cos 0
Class Map match-any c1
Match cos 1
Class Map match-any c2
Match cos 2
Class Map match-any c3
Match cos 3