6Access Control Lists (ACLs)This chapter describes access control lists (ACLs), prefix lists, and route-maps.At their simplest, access control lists (ACLs), prefix lists, and route-maps permit or deny traffic based onMAC and/or IP addresses. This chapter describes implementing IP ACLs, IP prefix lists and route-maps.For MAC ACLS, refer to Layer 2.An ACL is essentially a filter containing some criteria to match (examine IP, transmission control protocol[TCP], or user datagram protocol [UDP] packets) and an action to take (permit or deny). ACLs areprocessed in sequence so that if a packet does not match the criterion in the first filter, the second filter(if configured) is applied. When a packet matches a filter, the switch drops or forwards the packet basedon the filter’s specified action. If the packet does not match any of the filters in the ACL, the packet isdropped (implicit deny).The number of ACLs supported on a system depends on your content addressable memory (CAM) size.For more information, refer to User Configurable CAM Allocation and CAM Optimization. For completeCAM profiling information, refer to Content Addressable Memory (CAM).IP Access Control Lists (ACLs)In Dell Networking switch/routers, you can create two different types of IP ACLs: standard or extended.A standard ACL filters packets based on the source IP packet. An extended ACL filters traffic based on thefollowing criteria:• IP protocol number• Source IP address• Destination IP address• Source TCP port number• Destination TCP port number• Source UDP port number• Destination UDP port numberFor more information about ACL options, refer to the Dell Networking OS Command Reference Guide.For extended ACL, TCP, and UDP filters, you can match criteria on specific or ranges of TCP or UDPports. For extended ACL TCP filters, you can also match criteria on established TCP sessions.When creating an access list, the sequence of the filters is important. You have a choice of assigningsequence numbers to the filters as you enter them, or the Dell Networking Operating System (OS) assignsnumbers in the order the filters are created. The sequence numbers are listed in the display output of theshow config and show ip accounting access-list commands.Ingress and egress Hot Lock ACLs allow you to append or delete new rules into an existing ACL (alreadywritten into CAM) without disrupting traffic flow. Existing entries in the CAM are shuffled toAccess Control Lists (ACLs) 95
