Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

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 Dell Networking OS 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 255.

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 gig 1/0
                                 Dell(conf-if-gi-1/0)#service-policy input pmap