CCNA Routing and Switching Study Guide by Todd Lammle

Author:Todd Lammle
Language: eng
Format: epub
Publisher: Wiley
Published: 2013-09-14T16:00:00+00:00

We’ll cover these types of access lists in more depth later in the chapter.

Once you create an access list, it’s not really going to do anything until you apply it. Yes, they’re there on the router, but they’re inactive until you tell that router what to do with them. To use an access list as a packet filter, you need to apply it to an interface on the router where you want the traffic filtered. And you’ve got to specify which direction of traffic you want the access list applied to. There’s a good reason for this—you may want different controls in place for traffic leaving your enterprise destined for the Internet than you’d want for traffic coming into your enterprise from the Internet. So, by specifying the direction of traffic, you can and must use different access lists for inbound and outbound traffic on a single interface:

Inbound access lists When an access list is applied to inbound packets on an interface, those packets are processed through the access list before being routed to the outbound interface. Any packets that are denied won’t be routed because they’re discarded before the routing process is invoked.

Outbound access lists When an access list is applied to outbound packets on an interface, packets are routed to the outbound interface and then processed through the access list before being queued.

There are some general access-list guidelines that you should keep in mind when creating and implementing access lists on a router:

You can assign only one access list per interface per protocol per direction. This means that when applying IP access lists, you can have only one inbound access list and one outbound access list per interface.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.