Administrator Guide

Determine the Order in which ACLs are Used to Classify Traffic
When you link class-maps to queues using the service-queue command, the system matches the class-maps according to queue
priority (queue numbers closer to 0 have lower priorities).
As shown in the following example, 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. The order can range from 0 to 254. The system 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.
Example of the order Keyword to Determine ACL Sequence
Dell(conf)#ip access-list standard acl1
Dell(config-std-nacl)#permit 20.0.0.0/8
Dell(config-std-nacl)#exit
Dell(conf)#ip access-list standard acl2
Dell(config-std-nacl)#permit 20.1.1.0/24 order 0
Dell(config-std-nacl)#exit
Dell(conf)#class-map match-all cmap1
Dell(conf-class-map)#match ip access-group acl1
Dell(conf-class-map)#exit
Dell(conf)#class-map match-all cmap2
Dell(conf-class-map)#match ip access-group acl2
Dell(conf-class-map)#exit
Dell(conf)#policy-map-input pmap
Dell(conf-policy-map-in)#service-queue 7 class-map cmap1
Dell(conf-policy-map-in)#service-queue 4 class-map cmap2
Dell(conf-policy-map-in)#exit
Dell(conf)#interface tengig 1/0
Dell(conf-if-te-1/0)#service-policy input pmap
ACL Optimization to Increase Number of
Supported IPv4 ACLs
You can configure the Dell EMC Networking OS to support more number of IPv4 ACLs.
Restrictions for ACL Optimization
After you enable ACL optimization, the system does not support the following features:
• Mirroring dropped packets
• Ability to specify filtering for routed traffic only
• ACLs applied on physical ports with VRF ranges
• ACLs with filter parameters such as DSCP and ECN
• PIM VLT
• Filtering noninitial fragments of a datagram
If your ACL rules contain the following keywords, the system accepts the configuration and shows a message stating that these features
are not supported and ignores the configuration.
• ttl
• fragments
• no-drop
• dscp
• ecn
Access Control Lists (ACLs)
107