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Recently I jumped into the high banwidth wagon (cable). My isp came to install it and asked for the mac address of my computer.

1. What is the MAC Address?
2. Why my ISP needs it?
3. How can I connect my laptop and my brother's computer through a router to the cable modem?

Thanks in advance!!!

ISP shouldn't need your MAC address. The MAC address stands for Media Access Control Address. It is a unique identifier for each node on a network... basically it's a hardware specific IP address for the network card in your computer that allows everything else on the network to find it.

Your cable modem has one as well which the ISP had to authorize or authenticate to connect to the network.

When you ask general questions, tough to help. So let's clear some things up.

What ISP?
What Operating System do both computers have?
How were you connecting to the internet before (DSL, Dialup)? With which ISP?
What router?

Your ISP might have asked for the MAC address because they want to discourage you from using a router. This means they want to charge you on a per computer/per seat basis.

Assuming both your ciomputers have NICs (network intergace cards, plug bigger than a typical phone jack) just plug it into the router. Each computer goes into a separate port in the router.

Cable modem->Cat 5/Ethernet cable->Router->Separate Cables from Router to Desktop and Laptop.

Reboot both and you should be OK assuming you have windows 2000 or windows XP.

The ISP probably wanted to know the MAC address of your modem. To connect both computers, you can attach the modem to the "Internet" or "WAN" port on the router. You can manually select the MAC address that the router uses if you want. You can then attach both computers to the router. It will appear to the modem that only one computer is attached, but both computers will have internet access. This is roughly how I set up my cable internet connection at home.

1. ISP = Centennial
2. Both are running on XP Home
3. Dial-up, gneric company
4. a linksys, don't remember which model.

When they came to make the installation they asked for the Mac address and wrote it on the invoce including the mac address of the cable modem. I noticed that if I change the mac of my pc the internet won't work. The cable modem is a surfboard and it is conected to the computer through the ethernet card. I already conected the cable modem to the WAN conection of the router with no luck. Those this has to do with the mac address thing?

Does the router automatically set its own MAC address, or do you have it set to a custom MAC address? On my router (not Linksys), I can set the router to use its own MAC address, or I can manually configure it to use whatever MAC address I want.

I'm not sure, I'll have to check. Although it came with a sticker with a serial number and a the MAC Address. It was on the bottom side of the router.

OK the router model number is:
Linksys
Instant BroadBand Series
EtheFast Cable / DSL Router
Model BEFSR41

And the cable modem is:
Motorola
SB5100
SURFboard