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Using 2 NICs

W

WGM

noobie
Joined
May 7, 2007
Messages
20
So, here is what I want to do...

I have a machine that has 2 NICs in it. One NIC is connected to the LAN here for access to resources like email, RDP, shared drives, etc... The 2nd NIC is for internet access only.

Both NICs are assigned IPs from DHCP. NIC1 is the LAN adapter and NIC2 is hooked to a broadband router.

So, when both NICs are enabled, the NIC connected to the LAN stops working.

Basically what I want to do is have access to both networks simultaneously. It is important however that the networks remain separate.

Is there a simple way to accomplish this?
 
I think what we are looking at is a limitation of the TCP/IP stack in the OS more so than the adapter itself. I also am beginning to think we are not seeing some information here.

What is the purpose of the duel nick config where one can not see the other? Are you trying to SSH into your work computer from home or vise versa?

Tell us more about the use you are trying to get out of the duel nick config.

I know in Linux variant OS's it can handle multiple nicks quite readily from my expirence with AIX. Sometimes routing tables would get confused but it would not just disable one of the nicks.

Are they having a hardware conflict at all?
 
Grimlaking said:
I think what we are looking at is a limitation of the TCP/IP stack in the OS more so than the adapter itself. I also am beginning to think we are not seeing some information here.

What is the purpose of the duel nick config where one can not see the other? Are you trying to SSH into your work computer from home or vise versa?
Click to expand...
No, just using one network for internet access and one for other resources.

Grimlaking said:
Tell us more about the use you are trying to get out of the duel nick config.
Click to expand...
Very simply don't want to use the LAN connection for internet access. The secondary NIC is hooked to a T1, and I would like to utilize it.

Grimlaking said:
I know in Linux variant OS's it can handle multiple nicks quite readily from my expirence with AIX. Sometimes routing tables would get confused but it would not just disable one of the nicks.
Click to expand...
Don't really have the option of a *nix client right now.

Grimlaking said:
Are they having a hardware conflict at all?
Click to expand...
No, both NICs obtain an IP address from their respective DHCP server.
 
would you mind bringing up both interfaces and just copying and pasting the full routing table for us to look at?
 
Xipher said:
would you mind bringing up both interfaces and just copying and pasting the full routing table for us to look at?
Click to expand...

Alright.

Untitled-1.png
 
I don't think you need to fool with the routing tables directly. Just change the order of the binding and Windows will fix up the routing for you.

At least, that's the advice I got in the Multihome XP on a Windows Domain thread, and I ended up getting it working.
 
Looking at that routing table, the first thing I would try is raising the metric on the 10.230.x.x network to 20 or 30.
 
The metric is used by routing protocols to determine which is the "best" path to take given more than one choice of path to a given destination. Basically, setting it to 20 or 30 strongly discourages Windows from using that NIC - instead it will wait a bit and retry the much lower metric path if there was a momentary problem with using it in the first place.
 
Qualm said:
The metric is used by routing protocols to determine which is the "best" path to take given more than one choice of path to a given destination. Basically, setting it to 20 or 30 strongly discourages Windows from using that NIC - instead it will wait a bit and retry the much lower metric path if there was a momentary problem with using it in the first place.
Click to expand...

Perhaps you missed my intent.

I want traffic to flow to each NIC freely, I just want to be able to specify which traffic goes where. Make sense?
 
Why is your 10 network so huge? 255.255.254.0 ? 10.230.4.1 to 10.230.5.254

Do all the devices on the 10 network have the same mask (255.255.254.0), gateway and within the same subnet?

You mention your networks are 192.168.x.x and 10.230.x.x but they are realy 192.168.0.x and 10.230.4.x - 10.230.5.x

Are we dealing with a case of the fat fingers?
 
WGM said:
No, both NICs obtain an IP address from their respective DHCP server.
Click to expand...

For dual homing to work, you need a static IP with no gateway entry on the internal side NIC, and routing statements for all your internal network IP ranges.

You internal NIC will need to be set up like

IP 192.168.0.4
Subnet 255.255.255.0
Gateway: (this MUST be blank)

Your current DNS and WINS settings.

Then you will need to know all the internal ranges for your interior network segments.

If all the interior network segments are 192.168.x.x, you just need the following statement:

route add 192.168.0.0 MASK 255.255.0.0 192.168.0.1 /persistent

That will cause all traffic destined for 192.168.x.x addresses to go through the internal card and the statement will survive reboots. Traffic to any other network will go through the Internet facing card due to its being the default gateway and having the 0.0.0.0 0.0.0.0 routing statement associated with it. Right now, because that interface has a metric of 2 and the a 192.168.0.4 interface has a metric of 1 for that same statement, all your traffic will go through the internal interface.
 
I'm dual-homed with DCHP on the internal network and on the external network, no problem. (At least, I'm pretty sure I do.)
 
moetop said:
Why is your 10 network so huge? 255.255.254.0 ? 10.230.4.1 to 10.230.5.254

Do all the devices on the 10 network have the same mask (255.255.254.0), gateway and within the same subnet?

You mention your networks are 192.168.x.x and 10.230.x.x but they are realy 192.168.0.x and 10.230.4.x - 10.230.5.x

Are we dealing with a case of the fat fingers?
Click to expand...
This is at work, that's why the range is so large.

mikeblas said:
I'm dual-homed with DCHP on the internal network and on the external network, no problem. (At least, I'm pretty sure I do.)
Click to expand...
Would you mind posting your routes, Mike?

How did you get this to work?
 
WGM said:
This is at work, that's why the range is so large.
Click to expand...

A business network...and direct intenet access from your machine. Hmmm.... The IT manager have an issue with this? Quite a security risk. Or...to bypass content filtering rules?
 
mikeblas said:
I'm dual-homed with DCHP on the internal network and on the external network, no problem. (At least, I'm pretty sure I do.)
Click to expand...

No problem except two 0.0.0.0 0.0.0.0 route entries with different metrics on different interfaces keeping your traffic from working the way you want it to work. That will remain a problem as long as DHCP is enabled on both interfaces.
 
WGM said:
Perhaps you missed my intent.

I want traffic to flow to each NIC freely, I just want to be able to specify which traffic goes where. Make sense?
Click to expand...

Yes, but I believe I understood your intent.

The problem, as Nessus just pointed out, is that you have TWO routes to 0.0.0.0 ("anywhere else") with uncomfortably close metrics (in my estimation). The first thing I would suggest - did suggest - is changing the metric of one of the routes to 0.0.0.0 to a high enough number that Windows will not use it.

Being able to "specify which traffic goes where" implies that you are going create routing rules - what routes do you think you need beyond what Windows has already set up through ARP discovery?
 
WGM said:
Would you mind posting your routes, Mike?

How did you get this to work?
Click to expand...
I think most of the details are in the thread I linked to. I'm moving house, so the machine involved is down right now. I'll try to post the settings I used when it comes back up ...
 
YeOldeStonecat said:
A business network...and direct intenet access from your machine. Hmmm.... The IT manager have an issue with this? Quite a security risk. Or...to bypass content filtering rules?
Click to expand...
I am the IT Manager. Thanks for the concern. :rolleyes:

mikeblas said:
I think most of the details are in the thread I linked to. I'm moving house, so the machine involved is down right now. I'll try to post the settings I used when it comes back up ...
Click to expand...
Ok, I'll give it another look. Thanks, Mike.
 
i was able to do this on my xp sp2 machine as well with a wired and wireless, wireless was connected to the internet and the wired was connected to a switch did the same on my laptop, then i was able access the internet with both using wireless and transfered files between the two computer, sounds like this is the setup you are looking for, could be wrong, im at work right and i can never think straight at work
 
I finally got that machine installed again. It turns out the inside connection has no gateway address configured and is using a static IP address. The outside address is DHCP provided from the modem.
 
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