Standard vs. Extended ACLs

A standard ACL allows you to prioritize traffic by the Source IP address.

An extended ACL provides greater control over what traffic is prioritized. Extended ACLs can use any or all of the following parameters:

• Source IP address
• Destination IP address
• TCP/UDP Source port
• TCP/UDP Destination port.
• Protocol ID (RFC1700)

These five parameters are referred to as a "5 Tuple". Source or destination addresses allow you to prioritize traffic between any combination of host, subnet, and network addresses.

Further, if you specify a source or destination TCP/UDP port, you can prioritize specific traffic between hosts on two different networks. For example, you could increase the priority of Voice Over IP (VoIP) traffic between two subnets in a call center by specifying the UDP port number used by the phone system.

Note: If you specify TCP or UDP port numbers, you must specify Protocol ID 6 or 17 respectively. Failure to specify the Protocol ID number will result in an error message and the ACL will not be created.

Using a Protocol ID, you can prioritize traffic based on the Protocol ID number. RFC 1700 lists Protocol ID numbers. You could, for example, block all RSVP traffic (Protocol ID 46) through the router.