Inbound Vs Outbound access-list question

[fmatrine]

Hi All,

We hv a internet router with internet leased line connectivity.

I want to put access list for filtering unwanted traffic.

I will put access-list in inbound direction on the fastethernet interface of the router and in the outbound direction on the serial interface connected to ISP (Internet leased line).

As per my knowledge inbound means it will filter traffic coming from internet in to my local network and outbound means it will filter the traffic going out from my LAN to internet ... How true is this statement...

Pls guide with the actual flow of inbound vs outbound access-list

Regards

[Georg Pauwen]

Hello,

´inbound´ and ´outbound´ are referred to as referenced from the viewpoint of the router. There is a document on CCO which explains the concepts quite clearly, have a look at the link below:

Configuring IP Access Lists

Define In, Out, Source, and Destination

http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_tech_note09186a00800a5b9a.shtml#sourcedefine

HTH,

GP

[Richard Burts]

The link that Georg posted is good and has a nice definition of in and out and of source and of destination.

To expand slightly on his answer, for most of us when we talk about filtering unwanted traffic the most important thing is to filter traffic coming to you from the ISP. This would be an inbound filter on the serial. Perhaps the second most important thing is to filter what you are sending to the ISP which would be an outbound filter on the serial. It may or may not be important what is sent and recieved on the LAN interface where your users are located.

HTH

Rick