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Old 05-30-2007, 12:30 PM   #1
rdgreenlaw
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Registered: May 2007
Distribution: Ubuntu 14.04 LTS
Posts: 59

Rep: Reputation: 16
Question Adding site blocking to an existing network


I have a linux server and 5 Microsoft PCs connected to the internet through a switch and router (DSL.) I currently allow any network traffic to get to the internet, but would like to block access to some sites.

My setup looks like this:

[HTML]

internet
|
DSL Router
|
s w i t c h
| | | | | |
server pc1 pc2 pc3 pc4 pc5
[/HTML]
The server contains only one NIC. I would like to keep the hardware the same and provide all blocking by software if possible.

I need to know what software I should be using, and how to configure it. Any example configuration or pointer to a website that provides example confugurations would be very helpful.

Thanks,
 
Old 05-31-2007, 03:20 AM   #2
cyberfishee
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Registered: Mar 2005
Distribution: Debian Testing
Posts: 133

Rep: Reputation: 15
it is not possible without obscure configuration and severe performance penalty

the way i would imagine this can be done is to use a feature known as IP Aliasing, essentially emulating two network cards on the server, one connecting to the router and therefore to the internet, and the other one to the internal network

then you can configure the server to run as a gateway (IP masquerading), and configure the clients to use the server as the gateway

in that case you will be able to do the filtering on the server using iptables

but as i mentioned earlier, there will be a severe performance hit, because of the number of collisions and maybe other factors i am not aware of, in the server's physical network card

a better option is to add another PCI network card to the server, and connect the network like this:

internet
|
server
|
switch
|
clients

in that case the linux server will act as the router, and the router you are using now will not be necessary

btw, that is how my home network is set up now

here is a howto that i found helpful http://tldp.org/HOWTO/IP-Masquerade-HOWTO/
it looks very long but you can just read the relevant parts, it is very thorough, too
 
  


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