How can i control who are the users that use my shared internet connection from my pc not theirs?

i have a 8 pc's network using ip range 100.100.100.* and i have internet connection from a neighbour through a switch and i have two ethernet cards one for the local area and one for the internet and iam sharing internet so if any other pc set ip's to automatic it will use the internet two the problem is that i want just two pcs only to use it how can i do that without doing anything on the other computers


it is like making my pc allow these just two pc's only to use my shared internet connection how can i do something like this


all network is using windows xp pro sp2 and we have one 16 port switch d-link please i want something simple and if there is any software please provide where i can download it from please help cause the person giving me internet said that they are all connected and downloading causing slow connection for him and he will cut it from me so please helpHow can i control who are the users that use my shared internet connection from my pc not theirs?
A possible solution is to remove the default gateway from the machines that you do not want to access the internet or even better remove the DNS entries as well this way they will never resolve internet names.





NB this may require setting up static IP addresses for these devices. If they are smart enough they could also put them back on later (You may have to remove admin rights to stop them doing that)





Note even without DG and DNS all machines will still be able to communicate with devices in the same LAN

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