Web Management Guide-R07

Table Of Contents
Chapter 12
| Security Measures
Access Control Lists
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Access Control Lists
Access Control Lists (ACL) provide ingress packet filtering for IPv4/IPv6 frames
(based on address, protocol, Layer 4 protocol port number or TCP control code),
IPv6 frames (based on address, DSCP traffic class, ), 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 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:
ACLs only filter ingress packets or frames.
The maximum number of ACLs is 256.
The maximum number of rules per system is 512 rules.
An ACL can have up to 128 rules.
The number of ACLs that can be bound to the switch ports is limited to the
following:
128 MAC ACLs I
128 IP ACLs (including Standard and Extended ACLs)
64 IPv6 (Standard ACLs, and IPv6 Extended ACLs)
The maximum number of rules (Access Control Entries, or ACEs) stated 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
compression is disabled, the ACL would occupy (128*n) entries of TCAM, using
up nearly all of the hardware resources. When using compression, the 128 ACEs