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vamshikrishna · Feb 16, 2006, 12:07 AM

Hi guys it would be great if some one can clear my doubt my question is first of all I would like to know something about mac addresses and can we have 2 mac addresses and 2 ip adresses for a single computer if its possible can you guys please tell me how to do it... thnx a lot:)

LTheobald · Feb 16, 2006, 02:32 AM

Info on MAC addresses

As far as my understanding goes:

2 MAC addresses: Yes. If you have two network cards, then they will both have a different MAC address (due to them being hardware related).

2 IP addresses: No

This leads to the question - why? Why would you want two IP address?

vamshikrishna · Feb 16, 2006, 07:03 AM

Thanks a lot Ltheobald I was trying to know whether its possible to have multiple macs and multiple ips anyway is it not possible to have 2 mac addresses for a single network card am a newbie don't mind if I post foolish question:)

ScottGem · Feb 16, 2006, 07:05 AM

A MAC address is a hardware encoded unique address generally encoded into the network adapter. Therefore, you could not have multiples for a single card.

phillysteakandcheese · Feb 16, 2006, 08:54 AM

Just as a curiousity...
Windows stores the MAC address in the Windows registry, so if you manually edited the registry, you could fool Windows into thinking the NIC does have a different MAC address. ;)

I haven't tried this, but...
Certain ISP's make you register your MAC address. So if you could fool windows into sending an already registered MAC address, you could get around having to call the ISP and register a MAC for every device you're connecting to their network.

NeedKarma · Feb 16, 2006, 09:05 AM

Originally Posted by phillysteakandcheese

Certain ISP's make you register your MAC address.

I didn't know this. Thank god my ISP doesn't do that as I have hooked a variety of PCs to my dsl connection for tech support purposes.

Back to the question at hand. If you had a dual homed computer you would indeed have 2 network cards. As for 2 IPs, I'm not sure.

ScottGem · Feb 16, 2006, 09:44 AM

Originally Posted by NeedKarma

I didn't know this. Thank god my ISP doesn't do that as I have hooked a variety of PCs to my dsl connection for tech support purposes.

Yes, some broadband ISPs do this to prevent people from just going out and using someone else's broadband modem. But the MAC address they are registering is the modem's address, not a PC's address.

NeedKarma · Feb 16, 2006, 10:02 AM

Originally Posted by ScottGem

Yes, some broadband ISPs do this to prevent people from just going out and using someone else's broadband modem. But the MAC address they are registering is the modem's address, not a PC's address.

I stand corrected. Thanks.

ScottGem · Feb 16, 2006, 10:13 AM

You may sit :D

StuMegu · Feb 16, 2006, 12:10 PM

If you have two network cards, you can have two IP addresses (one per card), this is how internet connection sharing works on windows 2000/XP machines one card is connected to modem on one ip address and the other the local network.

If you wanted to have both ip addresses in the same range it might cause problems due to the computer name being duplicated.

On the mac addresses and ISP's they do register your mac address, it could be a router address or a modem linked to your network card on your machine. A lot of cable modems (mine included) will clone your PC mac address to get access to the ISP!