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CCNA 2 v3.1 Module 11 Access Control Lists (ACLs). Objectives. What are ACLs?. ACLs are lists of conditions used to test network traffic that tries to travel across a router interface. These lists tell the router what types of packets to accept or deny. How ACLs Work.
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What are ACLs? • ACLs are lists of conditions used to test network traffic that tries to travel across a router interface. These lists tell the router what types of packets to accept or deny.
access-list number Wildcard Mask Apply to all Incoming packets Apply ACL #2 to interface e0 Define an ACL & Apply it Deny all packets from 172.16.1.1
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
Destination IP addr. Source IP addr plus wildcard Extended ACLs
單一主機 Named ACLs
Placing ACLs • Standard ACLs should be placed close to the destination. • Extended ACLs should be placed close to the source.
Firewalls A firewall is an architectural structure that exists between the user and the outside world to protect the internal network from intruders.