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Here is my setup: Computer A, Computer B, Computer C and a router. All have internet access.

A and B are wired to router. Computer C is using wireless. I need to make Computer C able to access B only but not A. Is that possible? Can I achieve that by changing router settings? Thanks a lot.

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What operating system(s) are you using on each of the computers? What do you need to access on Computer B? File share? Or remote control? – Raystafarian Feb 26 '12 at 23:26
Why not use a firewall on A? – tjameson Feb 26 '12 at 23:28
Computer C is win 7 and A and B are XP. I need to have file share on computer B from Computer C. – Rouge Feb 26 '12 at 23:46
Can Firewall achieve this? built in firewall in computer or router? – Rouge Feb 26 '12 at 23:46
up vote 1 down vote accepted

On your router, configure it so that it gives Computer C a fixed IP address. Some routers call this "IP Reservations" or similar. Then configure the firewall on computer A to reject all connections from Computer C's address. You may be able to accomplish this on your router, depending on the capabilities of its firmware, but you can definitely accomplish it by configuring firewall settings on Computer A.

You could also make sure Computer A has strong passwords on all accounts and isn't running vulnerable software or software allowing anyone to access files on the system.

If computer C is likely to change its MAC address in an adversarial manner, then one option is to have a separate wired and wireless router, and configure its DHCP server to hand out a different range of addresses from your wired router. You can then tell Computer A's firewall to reject any connection from any IP in the wireless range.

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First off, set up file sharing on the 3 computers to only allow the access you want. If you need more, use firewalls (which you should be using anyway, to protect everyone else on the Internet from having your computers hijacked by spammers).

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