ACL overview

An access control list (ACL) is a container for rules that permit or deny network traffic based on criteria that you specify.

When a frame or packet is received or sent, the device compares its header fields against the rules in applied ACLs. This comparison is done according to a rule sequence, which you can specify. Based on the comparison, the device either forwards or drops the frame or packet.

The benefits of ACLs include the following:

• Provide security and traffic management.
• Monitor network and user traffic.
• Save network resources by classifying traffic.
• Protect against denial of service (DOS) attacks.

Regarding the range of filtering options, there are two types of ACL:

• Standard ACLs — Permit, deny, or hard-drop traffic according to source address only.
• Extended ACLs — Permit, deny, or hard-drop traffic according to source and destination addresses, as well as other parameters. For example, in an extended ACL, you can also filter by one or more of the following:
  • Port name or number
  • Protocol, for example TCP/UDP port name or number
  • TCP flags

Note

Except on SLX 9740 devices, Egress ACLs do not support TCP flags.

For information on hardware-based filtering of IP subnet-based directed broadcast and network-address traffic, refer to "IP broadcast ACLs (bACLs)."