a "Router"

What is this thing he keeps talking about?

(and what's that other thing - the 'Switch')?

Introduction:

A Router is exactly what it says, it Routes Packets (the basic quantum of information on a computer network). Now you know that - how about a little more detail...

In 'general' a router is a box that has at minimum, two interfaces (holes in it, sockets)...

the "WAN" side is connected to the "Internet" (read this as the place all the bad-people are!)

the "LAN" side is connected to your 'HomeLAN' - and that is where (we hope) all the 'good people' are...

So - what happens is (in most (small home-based)) routers is that each and every packet that comes into the router from the WAN side is 'inspected' and compared to some 'rules' that are written (by you (typically un-safe), a guru(typically the safest), or you can use the default rules written by the manufacturer (safe). Each rule compares a number of parameters in the packet's header and/or contents (read this as the header is similar to a postal envelope, the contents is similar to what is inside the envelope (is it anthrax?)? and if those parameters match the parameters in the rule then it is either 'accepted' (passed on-to the LAN-side, or it is rejected (dropped - that is - it does not enter the LAN-side network)

Now - that's the basics, - on the 'high-end' big BIG routers in big corporations and/or on the Internet might have 4-8-16-64 "ports" and may route traffic between many WAN links and LAN links - but - if we're talking a "HomeLAN" router, then it typically has only two 'sides' or 'ports' _ one for the WAN (outside) and one for the LAN (inside)...

SO - What about my Linksys (or other brand) router that has six 'sockets' or 'holes' or 'places to plug things in...

Well - there are at least two 'logical' components in your box - one is a 'router' the other is a 'switch' - there's still only two 'logical' 'ports', one typically says "WAN" right on the back - the others typically say 0,1,2,3..... - and those are what we call "switch ports" - logically they are all on the LAN-side of the router. So the confusion here is that there's actually two functional entities in that box, and of course you'd have to read a lot of manuals (RTFM = Read The Funny Manual)... - to figure this out, but Bill can tell you in this short, sweet, web-page...

last updated: Saturday, 24 August 2002