Episode 06     The Easiest Ethernet LAN

In September of 2005, I found two modern laptop computers, both running Windows XP, and I found that both of them had Ethernet connectors, and I decided I wanted to create a really simple local area network LAN interconnection between the two of them, so that I could share disk files.

The interface equipment technique and methodology that I used will work more or less the same way for any pair of modern, Windows-based computers. Whether they are desktop or laptop, running Windows XP or Windows 2000 or Windows 98, the approach is pretty much the same.

So long as each of them has an Ethernet interface with the usual RJ45 connector, this approach will work. Connectors like that in North America look a lot like the kind of connectors we use with our telephones, but fatter.

In my case, for this exercise, the first of these computers was a Compaq laptop, and here is a picture of its Ethernet connector, clearly visible along the back edge. Note that the connector has two little Light Emitting Diodes: one is called the "Link Light", indicating that there is an Ethernet connection, and the other is called the "Ethernet Activity Light", which flashes whenever the Ethernet interface is sending or receiving data.

The second of the two computers is a Hewlett Packard laptop. Like the first, it also has a modern Ethernet connector; this one visible on the side. And just like the Compaq, it also has two LEDs. The one on the left indicates data activity, and the one on the right is a link light, indicating that a hardware connection is active.

To start this all off, I set up both machines side-by-side on a roomy table, and I allowed both of them to boot up Microsoft’s well-known Windows XP operating system, displaying a desktop in the usual manner.


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Episode 05     Ethernet Switches


Ethernet Switches are a lot like Ethernet Hubs; they look the same, and they wire into your network in the same places.

If you’ve seen the AskMisterWizard.com movie entitled, “Ethernet Hubs Explained,” then you already know a lot about Hubs, and you’re ready for this movie. If you haven’t seen that one yet, you ought to watch it first, because this movie explains the differences between Hubs and Switches based on what you learned in that movie.

Ethernet Hubs and Ethernet Switches are so similar, that they’re often mistaken for one another and are often sold as if each were the other. Nowadays, it’s getting harder and harder to buy Hubs because they are being replaced in the marketplace by Switches. And if you buy a box that’s labeled “Hub” in today’s marketplace, there’s a pretty good chance that it’s actually a Switch.

To further underscore the similarities between Hubs and Switches, when you first install a  Switch, it operates exactly like a Hub until it learns gradually about your local area network and applies its one new trick. Also, if your  Switch ever becomes confused by perverse activity on your network, it will revert back to operating exactly like a  Hub.

Remember from our previous discussions about how a Hub has no brain? It’s just a completely mindless device that merges several Ethernet connectors onto a single Ethernet segment, and any traffic seen on any connector is relayed or broadcast out on all of the connectors.

Well, an Ethernet Switch starts out doing exactly the same thing, but it has a teeny, tiny little brain. And as it relays information from the various connectors to all of the others, it gets gradually smarter about that. Its little microprocessor brain also listens to the messages coming in through all of those connectors, and it remembers the Ethernet addresses of the equipment connected to each connector. It accumulates all of this information into a little table and after a while, it knows which of your Ethernet devices are wired to which of its connectors.

Thereafter, instead of mindlessly transmitting everything to everybody, it only transmits messages to the connectors that are appropriate. This will make your small network a little bit more efficient. The truth is, if your network is really small, you will never notice the difference.


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Episode 04     Ethernet Hubs Explained

An Ethernet hub merges several Ethernet connectors onto a single Ethernet segment. This is an Ethernet hub:

It’s a very dumb device that merges one, or two, or three, or four Ethernet connectors onto a single Ethernet segment. Its intelligence comes at a very low level. It understands only Ethernet. It doesn’t know what IP is, and it doesn’t care. So we can say that it works beneath IP’s radar. Think of an Ethernet hub the same way you think of an old extension cord and multiple outlet strip.


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