i know this is kind of long but please read the whole thing, because I need some help i have some questions towards the end but you'll probably need to read the whole thing to see how this all happned. I recently edit/changed my M.A.C address for my Linksys Network card in windows XP using regedt32 not regedit. Many articles on google on how to do that. Just type change mac registry. Anyways It was very interesting. I was able to change my mac address not phsyicall of course but just as good as if it was. Anyways It was interesting because when I changed it I got a whole differnt ip address. And I was even logged on to a different sub net as well I hope I'm using the right terminalogy. for instance instead of 12.255.1.1-255 I was able to obtain a different ip address such as 12.255.8.1-255 each time i changed my mac address and was able to to get ip address ex. 12.255.1-14.1-255 hope that makes sense. Anyways heres the real interesting part. I got a MAC address scanner. It would scan my network 12.255.8.1-255 for MAC addresses. Well I was only able to get mac addresses for only 12.255.8.1-255 even though I put it to scan 12.255.1.1 - 12.255-14.255 it searched all of those numbers but I only got results for any computers in 12.255.8.1-255 so I changed my MAC address again, and I was able to get into 12.255.10.1-255 so I scanned whole network again, this time I didn't get reults for 12.255.8.1-255 I got results only for 12.255.10.1-255 which was really interesting to me. I know that means something and could be exploited more. Perhaps I am given more rights with in my local subnet mask then others. But its funny because i could keep changing my mac address and get into different subnet masks. Well keep reading there is some more very interesting stuff I found out about this!!!! So I figured the Server on ComCast/ATT end assigned you an ip address acording to your MAC address. I noticed that it would assign u the same ip address everytime for the same MAC address/ different mac address different ip address. So I got my friends MAC address who leaves down the street a few blocks. I asked him to turn off his computer and and un plug his cable modem. I then entered in his MAC address into my Registry, then disabled and then enabled my network card. For changes to take effect. He then booted up and had no internet. I check my IP address I had the same IP address as he did when he had internet as well as his MAC address. I kind of knew this would happen. Some of u may already did. But keep reading some more interesting stuff happend that I'm stumped on. So I was thinking wow I could pretty much get any one's IP and Mac address in my town, and when they logged of the next time they got back on they would have no internet. But anyways so I played with this for a day or so. Changing my MAC address to all kinds of different numbers and stuff and each time was sucessful and also I was getting some cool Ip addresses. Anyways well the fun soon stopped for some reason. Perhaps the Network Admin noticed something. I don't know what he did but now I'll change my MAC address, in my network card status it'll say invalid IP, So I'll click repair and that fails, But then I'll get a different IP address like I did before even though it Failed to repair, but no it wasn't 169 it looked to be valid. But None of my internet worked, and every time I tried to Repair the Ip address it would fail. So I changed it back to my real MAC address. And my interent still didn't work so I called up TEch Support I guess for some reason my hardware account was removed meaning I guess my cable modem wasn't on the system i had to re-register it. So I did that and My internet worked fine as long as I didn't change my mac address. Which is funny because I could change it before to all kinds of stuff and I'd just get a different IP address, As if I changed my network card. This is interesting because why can't I change it now and get internet still. Are they assingning me an IP address Via my Cable modem's MAC address? Any ideas what they may have did to make it so I can't do that anymore? All the input we can get on this would be great. Just trying to figure out what the Network Admins might have done or if theres any way around this. I also noticed that now when I change my Mac address that I get a private Ip address that starts with 169. but that might be something on my end but i'm thinking they changed some stuff on their end making it so I can't even get a new IP. This is another interesting fact. So I called up my friends house up the street. I got his MAC address again and asked him to log off and everything again like we did before. So I put in his MAC address and same stuff happend no internet. I only have 2 guesses maybe 3 to why this is happening. 1. They know my computer name and are restricting it to only my oringal mac address or something. or 2. They changed it so I'm only getting an IP address according to my Cable Modem's MAC address. or 3 they changed the settings for the whole system making it more secure. I"m just trying to figure out what they may have done or if theres some ways around it. So guyz give me all your ideas and thoughts or experinces. Maybe try it and see if it works for u. here are some links mac address scanner http://www.youngzsoft.net/cc-get-mac-address/download.htm http://www.klcconsulting.net/Change_MAC_w2k.htm - changing your mac 1 other though perhaps they are restriciting my IP range to only my 1 Ip address. So put your thoughts ideas or experince would be great. Thanks

Hmm, never did like sharing a bus with the neighbors. Why would they not use the modem's MAC in the first place? Switch modems with your friend. Then try your exploits on your friend's computer with your modem. And just in case anyone on the Internet does not know, MAC addresses are not good for indentification.

I think I found my problem, I was some invalid MAC addresses I recently found this note on the net Note: "00-00-00-00-00-00" is NOT a valid MAC address. Even though you spoofed your MAC address to "00-00-00-00-00-00," your network adapter will reject this MAC address, and your TRUE MAC address will remain. You must assign MAC address according to the IANA Ethernet-number assignment database. Here is a link http://www.iana.org/assignments/ethernet-numbers that may have been part of my problem. Perhaps my other problem was that, my friends cable modem wasn't completly turned off the 2nd time. Just his computer. In theory I believe you could take down a whole network with this. Suppose there is a business in town that has Comcast Cable Internet. and they say have 50 computers hooked through their server which is then connected to 1 Comcast Cable line. Lets say they shutdown everything at 6pm everynight including computer and cable modem. If you were you were to have the same Computer name and MAC address of that server and then logged onto ComCast it'd think it was that Business Server. So the next day the bussiness Boots up, No interenet. In theory I believe that could happen just a interesting security thought. But heres my question why could I only get MAC address for people only within the same subnet as me I hope i used the right terminology for that. so lets say i'm in 12.255.8.1-255 why can i only get mac address for 12.255.8 why not 12.255.9.1-255 I can if my ip address is changed to a number within 12.255.9 just wondering why I am restricted to only that. Any way around that, like is there anyway I could get a MAC address outside of my ISP?? Any thoughts or ideas would be great

There was a point in time when you had to register your MAC address with the cable ppl. Only That MAC address would get u an ip. So if you wanted to change the MAC(new comp, NIC), you had to call and register it with them. They remove this security requirement mainly because it was a pain, the hold times were horrible and the staff were poorly trained at doing so. And most ppl would care less about finding there MAC address, if they could find it at all. And helping ppl to find it was a miracle in itself.

"why could I only get MAC address for people only within the same subnet as me?" Don't you mean IP address. You do not get MAC addresses from your provider, you get IP addresses.