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Setting DSCP Values for Egress Packets Based on Flow
Match-any Layer 3 flows may have several match criteria. All flows that match at least one of the match criteria are mapped to
the same queue because they are in the same class map.
Setting a DSCP value from QOS-POLICY-IN mode (refer to Setting a DSCP Value for Egress Packets) assigns the same DSCP
value to all of the matching flows in the class-map.
The flow-based DSCP marking feature allows you to assign different DSCP to each match criteria.
● Create matching flows within a class map that have different DSCP values.
CLASS MAP mode
match set-ip-dscp
The values you set from CLASS-MAP mode override the value you set in the QoS input policy DSCP value. Packets matching
the rule are marked with the specified value.
Dell#show run class-map
!
class-map match-any example-flowbased-dscp
match ip access-group test set-ip-dscp 2
match ip access-group test1 set-ip-dscp 4
match ip precedence 7 set-ip-dscp 1
Dell#show run qos-policy-input
!
qos-policy-input flowbased
set ip-dscp 3
Displaying Configured Class Maps and Match Criteria
To display all class-maps or a specific class map, use the following command.
Dell Networking OS Behavior: An explicit “deny any" rule in a Layer 3 ACL used in a (match any or match all) class-map
creates a "default to Queue 0" entry in the CAM, which causes unintended traffic classification. In the following example, traffic
is classified in two Queues, 1 and 2. Class-map ClassAF1 is “match any,” and ClassAF2 is “match all”.
● Display all class-maps or a specific class map.
EXEC Privilege mode
show qos class-map
The following example shows incorrect traffic classifications.
Dell#show running-config policy-map-input
!
policy-map-input PolicyMapIn
service-queue 1 class-map ClassAF1 qos-policy QosPolicyIn-1
service-queue 2 class-map ClassAF2 qos-policy QosPolicyIn-2
Dell#show running-config class-map
!
class-map match-any ClassAF1
match ip access-group AF1-FB1 set-ip-dscp 10
match ip access-group AF1-FB2 set-ip-dscp 12
match ip dscp 10 set-ip-dscp 14
match ipv6 dscp 20 set-ip-dscp 14
!
class-map match-all ClassAF2
match ip access-group AF2
match ip dscp 18
Dell#show running-config ACL
!
ip access-list extended AF1-FB1
seq 5 permit ip host 23.64.0.2 any
seq 10 deny ip any any
!
ip access-list extended AF1-FB2
seq 5 permit ip host 23.64.0.3 any
seq 10 deny ip any any
Quality of Service (QoS)
619