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I have a need to set up network so I can use two ethernet cards inside one Windows (Windows XP SP2) based PC, one for internet connection, second, for internal LAN.

Network diagram

How should I configure each NIC, with what IP's, subnet masks and gateways, so I can use inernet on my PC and get in touch with devices on my LAN?

I have found that there are some sort of re routing nessesary inside my PC, but how does it work?

I have already set up some configuration already, but I can't use it together with PC #1 NIC #1 connected. I need to disconnect, to access NIC WEB interface. Current configuration:

Switch #1 and PC #1 NAS #2 are gigabit one's, so I could access NAS with gigabit speed.

PC #1 NIC #1

  • IP XX.XXX.162.106
  • SN
  • GW XX.XXX.162.105

PC #1 NIC #2

  • IP
  • SN
  • GW

NAS #1 NIC #1

  • IP
  • SN
  • GW

My question is - what exact configuration should I do for every NIC in this LAN, so it would work? Is it possible to achieve internet access for Laptop, that is inside that NIC #2 LAN (should I just set up basic ICS)?

share|improve this question
Why not just replace the PC with a router, and connect the PC to the router's LAN side along with the switch and other devices? – David Schwartz Dec 16 '12 at 16:25
@DavidSchwartz The question is about this specific case. Sure, If there was a spare router to put between internet and switch, I would have no question to ask... – Deele Dec 17 '12 at 0:49
up vote 2 down vote accepted

ICS will do exactly what you want: make the necessary routes alone and add dhcp.

share|improve this answer
Oh, OK, I will check ICS, it feels easiest way. – Deele Dec 16 '12 at 19:58
Sure it is the best way and easiest without adding an hardware router. However, as the PC#1 will be the router, it has to be turned on to have internet on the LAN. – laurent Dec 16 '12 at 20:55

Try adding this at command prompt after you are done with all interface config.

ROUTE ADD  MASK web_gateway_ip IF external_interface_name

I guess this should work with your config. Otherwise post your routing table output here

netstat -nr

Also check that you are not getting local DNS server IP from internal DHCP.

share|improve this answer
What is web_gateway_ip? Where do I get external_interface_name. I have no access to those devices, I'm guiding setup by chat/phone, but I can ask him to send me routing tables. Even if setting up ICS (to which I'm already familiar with) will solve, I want to know more about ROUTE stuff and how to use it. I had problems with it already in other environments... – Deele Dec 16 '12 at 20:03
@daya Certainly PC#1 is receiving its public IP from ISP DHCP so this default route ( is probably already registered. – laurent Dec 16 '12 at 21:04
@Deele web_gateway_ip is the IP of the router that will supply internet (your ISP gateway). In your case it is XX.XXX.162.105. In windows XP, to see the routing table, you issue route PRINT command from CMD window. route is the command you use to define/delete routes in the routing table. See… for details. – laurent Dec 16 '12 at 21:06

It will be helpful to describe what you want to achieve and what equipment you have.

Your diagram gives the impression that only the PC needs to connect to the internet. If that is the case the the answer by @daya is the right one.

If the other equipment also needs internet connection the I suggest you save yourself the trouble and get a cable/broadband router if the device that PC #1 connects to is not a router.

ICS is fine but the PC has to be turned on for the other devices to connect/b and it limits you to the subnet.

Update: You are not limited on the subnet. It requires an official registry hack described here - (Thanks to laurent)

share|improve this answer
Thanks for info. I know limits, the situation is like this, and I need solution for this, without adding more hardware at this moment. In the future there will be another router, and problem will be solved hardware-wise. – Deele Dec 16 '12 at 20:00
If I remember well, you can change the subnet used by ICS. Not sure about its size but anyways a /24 should be more than enough in this case!!! – laurent Dec 16 '12 at 21:15
@laurent Thats interesting, I didn't know that. It may come in handy sooner than I think. – vfclists Dec 16 '12 at 22:38

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