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I have a machine that is running two NIC cards for seperation of networks. My question is how secure this is and what other methods of isolation I could use for two networks on the same machine?

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closed as not a real question by Chopper3, Chris S May 2 '12 at 19:24

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

What's your goal from a security perspective, and what's your intent in plugging this machine in to both networks? – Shane Madden May 2 '12 at 18:50

As long as you dont bridge them, or route between them (or tunnel or anything simmilar), both networks will be isolated from eachother, but you'll have access to both.

Another option would be using a managed switch with different VLANs for each network and connecting your to a trunk port (if your machine supports VLANs).

With a question so vague, i cannot give a better answer.

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Thank you. My goal is to isolate the two networks. Being novice at this I was wondering what the best approach would be for network isolation? – Ken May 2 '12 at 18:59

Somewhere along the line of 'massively secure' and 'zero security', it all depends on the OS and its configuration - and you've not told us anything about this whatsoever.

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It is neither secure nor insecure. All routers have two NICs (even if only virtually), for instance. It does introduce additional security considerations, of course, but if you want to ensure the LANs remain disjoint, you have but ensure the machine is not forwarding packets or otherwise routing.

You could also define a firewall rule to prevent this, looking for packets to be forwarded, or packets inbound from an address on one network destined for an address on the other, and filtering them. In linux you could just set the default policy for the forward chain to drop, for instance. This would add a level of assurance that traffic was not being forwarded, with the possible benefit of being able to see if the machine is trying to forward it.

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