Cisco Confidential 1 © 2010 Cisco and/or its affiliates. All rights reserved. CCNA ACLs Deepdive February, 2012 Jaskaran Kalsi Assoc. Technical Manager Europe/CEE/RCIS Cisco Networking Academy

© 2011 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 CCNA & ACLs Packet Filtering & ACL Overview Standard ACL Configuration Extended ACL Configuration Demo & Summary

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3  Provide a brief review of ACLs.  Demonstrate a brief example of how ACLs can be administered.  Provide a brief description of the troubleshooting scenarios that are available.  Focus on the use of Packet Tracer as a simulation tool and create an interactive session where the audience troubleshoots and pre- configured network.

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Cisco Confidential 5  ACLs are an area that not only students struggle with but also instructors.  ACLs are covered in both CCNA Discovery & Exploration.  CCNA Exploration:  CCNA Exploration 4 - Chapter 5  ACL theory  ACL examples  Packet Tracer Activities

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6  Controls access to a network  Analyzes incoming and outgoing packets.  Either permits or denies them based on a predefined set of criteria.  Routers act as packet filters  Make decisions based on source & destination IP addresses.  Source port; Destination port; & protocols can also be a determining factors.  ACLs are sequential lists that include the following:  Permit statement.  Deny statements.  They extract info from the packet header and test it against the permit/deny rules.

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 Inbound ACLs Outbound ACLs

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10  Standard Access Control Lists  ACLs numbered 1-99 or  IPv4 & IPv6  Filter solely on Layer 3 source information  Extended Access Control Lists

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11  Standard ACLs - placed as close to the destination as possible  Extended ACLs - placed on routers as close as possible to the source that is being filtered.

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© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Task: Block host from gaining access on While must be able to communicate with other networks. All other computers from the network of must be able to connect with the network of R2>enable R2#configure terminal R2(config)#access-list 1 deny host R2(config)#access-list 1 permit any R2(config)#interface FastEthernet 0/1 R2(config-if)#ip access-group 1 out

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14  Usually range from and  Extended ACLs check sources & destination address; ports; & protocols.  Hence provide a greater range of control and enhance security.

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© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16  Reflexive ACLs  Dynamically allow reply packets  Work with TCP & UDP sessions initiated internally  Reduced exposure to spoofing and DoS attacks  Dynamic ACLs  Also known as ‘Lock-and-Key’ ACLs  Were available only for IP traffic  Dependent on Telnet connectivity, authentication, & E-ACLs  Time Based ACLs  Allow for access control based upon time of day, day of the week, or day of the month.

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17  Which three statements should be considered when applying ACLs to a Cisco router? (Choose three) a) Place generic ACL entries at the top of the ACL. b) Place more specific ACL entries at the top of the ACL. c) Router-generated packets pass through ACLs without filtering. d) ACLs always search for the most specific entry before taking any filtering action. e) An access list applied to any interface without a configured ACL allows all traffic to pass.

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Cisco Confidential 19

Thank you.