138 | IP Access Control Lists (ACL), Prefix Lists, and Route-mapsw w w . d e l l . c o m | s u p p o r t . d e l l . c o m Standard and Extended ACLs take up the same amount of CAM space. A single ACL rule uses 2 CAMentries whether it is identified as a Standard or Extended ACL.Determine the order in which ACLs are used to classify trafficWhen you link class-maps to queues using the command service-queue, FTOS matches the class-mapsaccording to queue priority (queue numbers closer to 0 have lower priorities). For example, in Figure 8-2,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 cmap1and are buffered in queue 7, though you intended for these packets to match positive against cmap2 and bebuffered in queue 4.In cases such as these, where class-maps with overlapping ACL rules are applied to different queues, usethe order keyword to specify the order in which you want to apply ACL rules, as shown in Figure 8-2. Theorder can range from 0 to 254. FTOS writes to the CAM ACL rules with lower order numbers (ordernumbers 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.Figure 8-2. Using the Order Keyword in ACLsIP Fragment HandlingFTOS supports a configurable option to explicitly deny IP fragmented packets, particularly second andsubsequent packets. It extends the existing ACL command syntax with the fragments keyword for allLayer 3 rules applicable to all Layer protocols (permit/deny ip/tcp/udp/icmp).• Both standard and extended ACLs support IP fragments.FTOS(conf)#ip access-list standard acl1FTOS(config-std-nacl)#permit 20.0.0.0/8FTOS(config-std-nacl)#exitFTOS(conf)#ip access-list standard acl2FTOS(config-std-nacl)#permit 20.1.1.0/24 order 0FTOS(config-std-nacl)#exitFTOS(conf)#class-map match-all cmap1FTOS(conf-class-map)#match ip access-group acl1FTOS(conf-class-map)#exitFTOS(conf)#class-map match-all cmap2FTOS(conf-class-map)#match ip access-group acl2FTOS(conf-class-map)#exitFTOS(conf)#policy-map-input pmapFTOS(conf-policy-map-in)#service-queue 7 class-map cmap1FTOS(conf-policy-map-in)#service-queue 4 class-map cmap2FTOS(conf-policy-map-in)#exitFTOS(conf)#interface gig 1/0FTOS(conf-if-gi-1/0)#service-policy input pmap
