Cisco Systems OL-6426-02 manual Access Lists

Appendix B Concepts

Access Lists

Access Lists

With basic standard and static extended access lists, you can approximate session filtering by using the established keyword with the permit command. The established keyword filters TCP packets based on whether the ACK or RST bits are set. (Set ACK or RST bits indicate that the packet is not the first in the session and the packet therefore belongs to an established session.) This filter criterion would be part of an access list applied permanently to an interface.

Cisco 1800 Series Integrated Services Routers (Fixed) Software Configuration Guide

OL-6426-02 B-11