In this white paper, we'll take a look at access control lists, often referred to as access lists or ACLs (sometimes pronounced "ackels"). In Cisco IOS, ACLs are used for many things, including but not limited to:
Filtering data packets (firewalling)
Controlling Telnet or SSH access to a router or switch
Filtering routing protocols
Specifying Quality of Service (QoS)
Controlling NAT (Network Address Translation)
The idea of an access list is straightforward: it permits some things, and denies others. What exactly is being “permitted” or “denied” v...