CCNA Cisco Certified Network Associate Study Guide - FTP Server

Access Lists
The proper use and configuration of access lists is a vital part of
router configuration because access lists are such vital networking accessories.
Contributing mightily to the efficiency and optimization of your network,
access lists give network managers a huge amount of control over
traffic flow throughout the internetwork. With access lists, managers can
gather basic statistics on packet flow and security policies can be implemented.
Sensitive devices can also be protected from unauthorized access.
Access lists can be used to permit or deny packets moving through the
router, permit or deny Telnet (VTY) access to or from a router, and create
dial-on demand (DDR) interesting traffic that triggers dialing to a remote
location.
In this chapter, we’ll discuss access lists for both TCP/IP and IPX, and
we’ll cover some of the tools available to test and monitor the functionality
of applied access lists.
Access lists are essentially lists of conditions that control access.
They’re powerful tools that control access both to and from network segments.
They can filter unwanted packets and be used to implement security
policies. With the right combination of access lists, network managers will
be armed with the power to enforce nearly any access policy they can invent.
The IP and IPX access lists work similarly—they’re both packet filters that
packets are compared with, categorized by, and acted upon. Once the lists
are built, they can be applied to either inbound or outbound traffic on any