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How to block clients by masking their subnet mask or changing their gateway information while forwarding any outward traffic from such clients to a specific proxy or server to display some message or captive portal ? What subnet mask and/or gateway information with static routes shall I use with them ?


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You won't be able to reliably control settings on client machines. You can set up the gateway to intercept all Port 80/443 traffic to go through a proxy, but it sounds like what you really want is a network access control system like PacketFence.

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Yes, we are using in-house developed NAC and we want to forward blocked machine to some sort of captive portal or at least show some message to them on how to unblock. Any ideas how ? I prefer to be able to do so on client machines not routers if possible – Geeko Jan 12 '11 at 8:43
You will only be able to do this if you have administrative rights to every client, and users do not. Even then, it's a pretty poor NAC and easy to bypass. – blueben Jan 12 '11 at 9:16

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