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we are working in a lab with set of 35 systems in college. my system is only ubuntu installed and i got the separate ip for my project purpose. and each one having the separate ip. but somebody else unknowingly use my ip to download movies and not allowing me to use internet for my project work. the network adminstrator is busy for 3 months. so i have to find a solution. so i need the solution for:

1) how to block others to use my ip even though i am not an network administrator(my ip:, proxy server is:

so could anyone please suggest me any software or any guide too prevent others from using my ip.

thank you.

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There is no effective way of doing this, especially as you are not a network admin (and even then, frankly, its still an issue). There is no way to stop someone typing whatever address they like into their computer. – RobM Jan 29 '11 at 11:07

If you're not the network administrator there's a limited number of things that you can do to avoid anyone using your IP, the only one I can think of is just leaving a small Ubuntu box behind with that IP assigned all the time.

Although if you can talk with the sysadmin you can convince him of doing one very simple thing, which is locking the traffic through that IP address to your computer MAC address (it's the unique hardware address that is given to your Ethernet card), this way if anyone else uses that IP they won't have any incoming or outgoing traffic and they'll eventually just flip to another one.

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There is software that can change the MAC address. In linux, you can change the MAC trivially, using ifconfig. – halp Jan 29 '11 at 14:15
Indeed halp, nonetheless this looks a lot more like casual IP assignment than sabotage. – lynxman Jan 29 '11 at 14:18

I am confused about what you are using a proxy server for. If you want firefox to use a proxy server, click Edit -> Preferences -> Advanced -> Network -> Settings

If you want your computer to have a specific IP address, you can try setting it as the static IP address in ubuntu

(System -> Preferences -> Network Connections -> click the name -> click edit -> IPv4 Settings -> change Method from Automatic to Manual -> add the address that you want)

Netmask is probably something like

Gateway is probably what you were calling proxy (

DNS Server is probably the same as the gateway (or use from google)

If someone else has your IP address, you wont be able to connect. You can run this over and over again until you are able to connect:

sudo ifconfig eth0 down


sudo ifconfig eth0 up

and it should connect once the other computer is disconnected.

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