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I am a newbie in the networking world and a little help would be appreciated in correctly configuring two NICs. I have searched your forum for multiple network card configurations, but none of them worked.

We have one PC (Win XP SP 2) - with network cards. One (native) uses the same network with other computers on the same floor and for Internet, and the other one is for using a special software upstairs on a different network. So two independent networks

Here is where the problem arises. Both of the NICs have static IPs. Native NIC for flr 1

However, Internet stops working after one or two days. I constantly have to change the IP to so on. And even that one expires in the next day. Any IP I put lasts for a day only.

What could be the cause? Automatic DNS and IP is not solving the issue. Thanks!

PS. Forgot to mention. There is another computer on flr 1 with Win 7 that houses 2 NICs. But it never has the same problem.... I am getting a white hair over this already...

PPS. Route Print in case it helps...

Interface List 
0x1 ........................... MS TCP Loopback interface 
0x2 ...00 04 75 7a d6 f2 ...... 3Com EtherLink XL 10/100 PCI For Complete PC Man 
agement NIC (3C905C-TX) - Packet Scheduler Miniport 
0x3 ...00 1a a0 c0 9e 4f ...... Broadcom NetXtreme 57xx Gigabit Controller - Pac 
ket Scheduler Miniport 
Active Routes: 
Network Destination        Netmask          Gateway       Interface  Metric
      20       1      20       20       20       20      20       20      20       20      20       1      1
Default Gateway: 
Persistent Routes: 
share|improve this question
The fact that you have two default gateways set is a problem. I am not sure if it is explains why you are loosing your config on one of the interfaces. Anyway, only one default gateway will be ever used. You probably remove the gateway from one of the interfaces. – Zoredache Dec 13 '10 at 21:22
BTW the addresses/network in the body of your question, are different from the addresses in your route print. You may want to fix that. – Zoredache Dec 13 '10 at 21:25
But they are two different networks though. I just checked the ip. They were exactly what I wrote in the body of this thread... – user63780 Dec 15 '10 at 21:41
@Zoredache, you should add that as an answer, having two DGs on different NICs seems to really screw with XP in very strange ways. – Chris S Mar 10 '11 at 13:23
I think Javlon mistakenly wrote "" (output of route print) as "" (in the question) – pepoluan Mar 10 '11 at 13:37

A question first: Look at the 2nd NIC (which connects to a 'special software' upstairs). Does its address lie on the same subnet as the 'special software'?

If it does: remove the Default Gateway from the 2nd NIC. The 1st NIC gets to keep its Default Gateway.

If it doesn't:

  1. Note the Default Gateway of the 2nd NIC (DG2 for short)

  2. Remove the Default Gateway setting of the 2nd NIC

  3. Enter the following command (on one line!):

    route -p add <subnet_of_special> mask <mask_of_special> <address of DG2>

  4. You might need to reboot.

Edit: This is a situation I also face in my office right now:

  • A certain workstation has 2 NICs; one connected to the office LAN, the other is a direct connection to an external site (the regulatory body of my company's industry, actually)

  • The internal LAN is The external site's address is 10.xx.yy.zz/24. BUT the 2nd NIC's address is; it must pass the external site's router with the address of to reach 10.xx.yy.zz

  • So, I delete the DG from the 2nd NIC and add an explicit static route like the above: route -p add 10.xx.yy.zz MASK

  • NIC1 maintains its DG of

  • Now packets for 10.xx.yy.zz will go out NIC2 and transferred via the router, while packets for the Internet will go out NIC1 (having the sole DG) toward the router.

share|improve this answer
@Chris 1) Javlon explained that they are two different networks. 2) Yes, which is why I tell him to remove the default gateway on the 2nd NIC. I told him above to add an explicit static route toward the 2nd gateway – pepoluan Mar 10 '11 at 13:24
@Chris : read my edit. Will that make sense to you now? – pepoluan Mar 10 '11 at 13:31
@Chris : nope. That is why I explicitly asked: "Does [the 2nd NIC's] address lie on the same subnet as the 'special software'?", and provided two options depending on the answer. In my situation, there are only 2 NICs also. But the destination of the 2nd NIC lies in a different subnet. – pepoluan Mar 10 '11 at 13:56

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