Reference Guide

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Access Control Lists (ACLs)
This chapter describes access control lists (ACLs), prefix lists, and route-maps.
• Access control lists (ACLs), Ingress IP and MAC ACLs , and Egress IP and MAC ACLs are supported on the
S4820T platform.
At their simplest, access control lists (ACLs), prefix lists, and route-maps permit or deny traffic based on MAC 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 are processed 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 based on the filter’s specified action. If the packet does not match any
of the filters in the ACL, the packet is dropped (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 complete CAM 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 the following
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 number
For more information about ACL options, refer to the FTOS Command Reference Guide .
For extended ACL, TCP, and UDP filters, you can match criteria on specific or ranges of TCP or UDP ports. 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 assigning sequence
numbers to the filters as you enter them, or the Dell Networking operating system (FTOS) assigns numbers in the order
the filters are created. The sequence numbers are listed in the display output of the
show 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 (already written into
CAM) without disrupting traffic flow. Existing entries in the CAM are shuffled to accommodate the new entries. Hot lock
ACLs are enabled by default and support both standard and extended ACLs and on all platforms.
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