Web Management Guide-R04

Table Of Contents
Chapter 12
| Security Measures
Access Control Lists
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Access Control Lists
Access Control Lists (ACL) provide packet filtering for IPv4/IPv6 frames (based on
address, protocol, Layer 4 protocol port number or TCP control code), IPv6 frames
(based on source or destination address), or any frames (based on MAC address or
Ethernet type). To filter incoming packets, first create an access list, add the
required rules, and then bind the list to a specific port.
Configuring Access Control Lists –
An ACL is a sequential list of permit or deny conditions that apply to IP addresses,
MAC addresses, or other more specific criteria. This switch tests ingress or egress
packets against the conditions in an ACL one by one. A packet will be accepted as
soon as it matches a permit rule, or dropped as soon as it matches a deny rule. If no
rules match, the packet is accepted.
Command Usage
The following restrictions apply to ACLs:
The maximum number of ACLs is 256.
The number of rules that can be configured for each ACL is as follows:
MAC ACLs - 256 rules maximum per ACL
IPv4 ACLs - 256 rules maximum per ACL
IPv6 ACLs - 128 rules maximum per ACL
An ACL can have up to the specified maximum number of rules. However, due
to resource restrictions, the average number of rules bound to the ports should
not exceed 20.
The maximum number of rules that can be bound to the ports is 64 for each of
the following list types: MAC ACLs, IP ACLs (including Standard and Extended
ACLs), IPv6 Standard ACLs, and IPv6 Extended ACLs.
The maximum number of rules (Access Control Entries, or ACEs) stated above is
the worst case scenario. In practice, the switch compresses the ACEs in TCAM (a
hardware table used to store ACEs), but the actual maximum number of ACEs
possible depends on too many factors to be precisely determined. It depends
on the amount of hardware resources reserved at runtime for this purpose.
Auto ACE Compression is a software feature used to compress all the ACEs of an
ACL to utilize hardware resources more efficiency. Without compression, one
ACE would occupy a fixed number of entries in TCAM. So if one ACL includes 25
ACEs, the ACL would need (25 * n) entries in TCAM, where “n” is the fixed
number of TCAM entries needed for one ACE. When compression is employed,
before writing the ACE into TCAM, the software compresses the ACEs to reduce
the number of required TCAM entries. For example, one ACL may include 128
ACEs which classify a continuous IP address range like 192.168.1.0~255. If