port ranges for multiple NIC cards

December 21, 2009 at 16:32:13
Specs: Windows

I would like to ask if a computer has multiple NIC cards, say two cards, and each has a different IP address assigned to it (192.168.100.x and 192.168.200.x), does that mean that each IP address can use the same port numbers (such as port 80 on both IP addresses)? In other words, each NIC can use its own range of port numbers (0-65535)?

second question
will there be a conflict if the two NIC cards were to use the same IP? I am thinking it will not work (tested it myself) but just wanted confirmation

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December 22, 2009 at 05:39:27
Second question first: Most definitely YES.

There can ever only be one instance of any IP address within a network.

Your first question is a little strange. Think about this, if you have a single NIC and are surfing the web and end up with 8 windows or tabs open, do you think that's a single instance of port 80 in use, or is it 8?

If you explained what it is you wish to try to do with the dual NIC's, we may better try to answer your question.

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December 22, 2009 at 17:47:59

sorry should have been more detailed, there are a few scenarios which I need some advice and help

For question one there are a few scenarios

Scenario One
If there is one program (say Program1) that needs to listen on the same ports for both NICs (different IPs), is that possible? Same instance listening on different IPs but same ports

Scenario Two
If there are two instances of the same program (again we call it Program1), that have to listen on the different IPs but same ports, is that possible?

Scenario Three
If there are two DIFFERENT programs listening on the different IPs but same ports, this should work right?

sorry again if my questions are very newbie-like

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December 23, 2009 at 07:33:06
1) I'm not a programmer so I can't answer this question. You may want to post it in the programming forum.

2) I suppose that's possible but, the you would have to be able to tell each instance of the program which interface to listen to. If you're running two separate instances of the same application, I have no idea if you could accomplish telling each instance to listen to a different interface.

3) yes

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December 23, 2009 at 17:13:10

Thanks for the reply. I will post it on other forums and see if anyone can help.

Thanks again for the help

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