Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 112

ipv4pbr 2 cam-acl-pe l2acl 3 ipv4acl 2 ipv6acl 2 ipv4qos 2 l2qos 1 ipmacacl 2 cam-acl-egress-pe l2acl 2 ipv4acl 2 ipv6acl 0 Implementing ACLs You can assign one IP ACL per physical or VLAN interface. If you do not assign an IP ACL to an interface, it is not used by the software in any other capacity. The number of entries allowed per ACL is hardware-dependent. If you enable counters on IP ACL rules that are already configured, those counters are reset when a new rule is inserted or prepended. If a rule is appended, the existing counters are not affected. This is applicable to the following features: • L2 Ingress Access list • L2 Egress Access list • L3 Egress Access list ACLs and VLANs There are some differences when assigning ACLs to a VLAN rather than a physical port. For example, when using a single port-pipe, if you apply an ACL to a VLAN, one copy of the ACL entries is installed in the ACL CAM on the port-pipe. The entry looks for the incoming VLAN in the packet. Whereas if you apply an ACL on individual ports of a VLAN, separate copies of the ACL entries are installed for each port belonging to a port-pipe. When you use the log keyword, the CP has to log the details about the packets that match. Depending on how many packets match the log entry and at what rate, the CP might become busy as it has to log these packets' details. However, the Route Processor (RP) is unaffected. This option is typically useful when debugging some problem related to control traffic. We have used this option numerous times in the field and have not encountered problems so far. ACL Optimization If an access list contains duplicate entries, the system deletes one entry to conserve CAM space. Standard and extended ACLs take up the same amount of CAM space. A single ACL rule uses two CAM entries whether it is identified as a standard or extended ACL. 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 Access Control Lists (ACLs) 112