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Determine the order in which ACLs are used to classify traffic
When you link class-maps to queues using the command service-queue, FTOS matches the class-maps
according to queue priority (queue numbers closer to 0 have lower priorities). For example, in
Figure 41-10, class-map cmap2 is matched against ingress packets before cmap1.
ACLs acl1 and acl2 have overlapping rules because the address range 20.1.1.0/24 is within 20.0.0.0/8.
Therefore, (without the keyword
order) packets within the range 20.1.1.0/24 match positive against cmap1
and are buffered in queue 7, though you intended for these packets to match positive against cmap2 and be
buffered in queue 4.
In cases such as these, where class-maps with overlapping ACL rules are applied to different queues, use
the
order keyword to specify the order in which you want to apply ACL rules, as shown in Figure 41-10.
The order can range from 0 to 254. FTOS writes to the CAM ACL rules with lower order numbers (order
numbers closer to 0) before rules with higher order numbers so that packets are matched as you intended.
By default, all ACL rules have an order of 254.
Set 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 since they are in the same class map. Setting a DSCP value from
QOS-POLICY-IN mode (see Set a DSCP value for egress packets on page 861) 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 CLASS-MAP mode using the option
set-ip-dscp with the
match command so that matching flows within a class map can have different DSCP values, as shown in
Figure 41-11. The values you set from CLASS-MAP mode override the value you QoS input policy DSCP
value, and packets matching the rule are marked with the specified value.
Figure 41-11. Marking Flows in the Same Queue with Different DSCP Values
Display configured class maps and match criteria
Display all class-maps or a specific class map using the command show qos class-map from EXEC
Privilege mode.
FTOS#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
FTOS#show run qos-policy-input
!
qos-policy-input flowbased
set ip-dscp 3
FTOS# show cam layer3 linecard 2 port-set 0
Cam Port Dscp Proto Tcp Src Dst SrcIp DstIp DSCP Queue
Index Flag Port Port Marking
-------------------------------------------------------------------------------------------
-----
16260 1 0 TCP 0x0 0 0 1.1.1.0/24 0.0.0.0/0 2 0
16261 1 0 UDP 0x0 0 0 2.2.2.2/32 0.0.0.0/0 4 0
16262 1 56 0 0x0 0 0 0.0.0.0/0 0.0.0.0/0 1 0
24451 1 0 0 0x0 0 0 0.0.0.0/0 0.0.0.0/0 - 0