1 © 2003 Cisco Systems, Inc. All rights reserved. CCNA 2 v3.0 Module 11 Access Control Lists (ACLs)

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444 © 2003, Cisco Systems, Inc. All rights reserved. Objectives Access control list fundamentals Access control lists (ACLs)

555 © 2003, Cisco Systems, Inc. All rights reserved. What are ACLs? ACLs are lists of instructions you apply to a router's interface to tell the router what kinds of packets to accept and what kinds to deny.

666 © 2003, Cisco Systems, Inc. All rights reserved. How ACLs Work

777 © 2003, Cisco Systems, Inc. All rights reserved. Protocols with ACLs Specified by Numbers

888 © 2003, Cisco Systems, Inc. All rights reserved. Creating ACLs

999 © 2003, Cisco Systems, Inc. All rights reserved. The Function of a Wildcard Mask

10 © 2003, Cisco Systems, Inc. All rights reserved. Verifying ACLs There are many show commands that will verify the content and placement of ACLs on the router. show ip interface show access-lists Show running-config

11 © 2003, Cisco Systems, Inc. All rights reserved. Standard ACLs

12 © 2003, Cisco Systems, Inc. All rights reserved. Extended ACLs

13 © 2003, Cisco Systems, Inc. All rights reserved. Named ACLs

14 © 2003, Cisco Systems, Inc. All rights reserved. Placing ACLs Standard ACLs should be placed close to the destination. Extended ACLs should be placed close to the source.

15 © 2003, Cisco Systems, Inc. All rights reserved. Firewalls A firewall is an architectural structure that exists between the user and the outside world to protect the internal network from intruders.

16 © 2003, Cisco Systems, Inc. All rights reserved. Restricting Virtual Terminal Access