Dell Force10 S55T S55 Configuration Guide FTOS 8.3.5.3 - Page 567

Figure 31-10. Using the Order Keyword in ACLs Force10(conf)#ip access-list standard acl1 Force10(config-std-nacl)#permit 20.0.0.0/8 Force10(config-std-nacl)#exit Force10(conf)#ip access-list standard acl2 Force10(config-std-nacl)#permit 20.1.1.0/24 order 0 Force10(config-std-nacl)#exit Force10(conf)#class-map match-all cmap1 Force10(conf-class-map)#match ip access-group acl1 Force10(conf-class-map)#exit Force10(conf)#class-map match-all cmap2 Force10(conf-class-map)#match ip access-group acl2 Force10(conf-class-map)#exit Force10(conf)#policy-map-input pmap Force10(conf-policy-map-in)#service-queue 7 class-map cmap1 Force10(conf-policy-map-in)#service-queue 4 class-map cmap2 Force10(conf-policy-map-in)#exit Force10(conf)#interface gig 1/0 Force10(conf-if-gi-1/0)#service-policy input pmap Create a Layer 2 class map All class maps are Layer 3 by default; you can create a Layer 2 class map by specifying the option layer2 with the class-map command. A Layer 2 class map differentiates traffic according to 802.1p value and/or characteristics defined in a MAC ACL. 1. Create a match-any class map using the command class-map match-any or a match-all class map using the command class-map match-all from CONFIGURATION mode, and enter the keyword layer2. 2. Once you create a class-map, FTOS places you in CLASS MAP mode. From this mode, specify your match criteria using the command match mac. Match-any class maps allow up to five access-lists, and match-all class-maps allow only one. You can match against only one VLAN ID. 3. After you specify your match criteria, link the class-map to a queue using the command service-queue from POLICY MAP mode. 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 31-10, 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 31-10. 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. Quality of Service | 567