Route problem in XP

Posted on 2009-05-17
Last Modified: 2012-05-07
I have a need to route all LAN traffic through a PC which would have monitoring software to check if all our internet traffic is legitimate and which clients are using it the most.

I am using a Windows  XP Pro SP3 machine with 2 NICs.
The public NIC (internet) is connecting direct to the internal IP ( of the ADSL router.
The LAN NIC is with the LAN clients using a DHCP server to get their IPs on the 192.168.10.x network

I have enabled IPenableRouter in the registry of the XP machine.
From the XP PC I can get internet access and also ping the clients on the 192.168.10.x network.

Internet sharing is NOT an option as it uses a class C network and would upset the LAN subnet particularly the fixed IP machines and printers etc.

How do I get the LAN clients to access the internet through the XP machine?
I assume that I would need a persistant route or two but am having difficulty working out exactly what is required  I have no experience in routing.

It is probably a very simple matter for the right person.
Any help would be greatly appreciated
Question by:HBB42
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LVL 19

Expert Comment

by:Mal Osborne
ID: 24405702
Routing is not enough here, you neen some software on the PC doing network address translation (NAT).  You could in theory get packets out OK, but then they have no way of being routed back to the correct machine without NAT in place.  

Internet sharing provides NAT. but there are other solutions. Using an XP box this way is a little unusual.  

Author Comment

ID: 24405728
Thanks for your reply.
Sorry to confuse you but the current ADSL router does NAT to the 192.168.10.x network and I understand that I would need to change the config of the ADSL router to redirect any packets destined for the 192.168.10.x network to the 192.168.1.x network which would then be routed to the 192.168.10.x network by the XP machine.
Hope this helps to clarify the situation and maybe you are right that i should be using other means but this option if it works is the most convenient.
LVL 26

Expert Comment

ID: 24406562
Wouldn't you just bridge the two NIC's in the XP machine?

On the XP machine, go into Control Panel / Network Connections.  While holding down the control key, click on each of the two XP NICs (the one to the internet, and the one that the rest of your network is talking to.)  Then, with both connections highlighted, right click, and select "Bridge Connections."
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Expert Comment

ID: 24406678

Author Comment

ID: 24410418
I tried making a bridge without success.
I read in an article that you can not use a bridge with a network NIC using ICS or ICF.
Any other suggestions appreciated
LVL 10

Expert Comment

ID: 24410719
assuming the xp machine is properly routing you need the lan machines to have the lan interface of the xp box as their default gateway, and a static route on the adsl router pointing at the ip of the xp boxes public nic.

The route in the adsl router will be .. netmask gateway .

Dont know how you configure routes in your model router, usually there is a tab for advanced network.

Your dhcp server needs to hand out the default route of the lan nic, dont know what your dhcp server is.

Author Comment

ID: 24420217
Thanks for all the comments so.
However none have solved my problem.
In my test environment i have made all IPs static (no DHCP)
Any other comments appreciated
LVL 10

Expert Comment

ID: 24420268
Does the router have a route to the LAN network range? It should be netmask gateway .

What make and model is the router?

What is the default gateway of the other pcs on the LAN network?

Author Comment

ID: 24420787
I put the static route on the router of mask but did not help
Router is  Billion BiPac 7402R2-M
DG of LAN PCs is
Attached is a dump of the route table of the XP machine with NO manual entries of my own if it helps
Thanks for your interest

Author Comment

ID: 24420869
Additional Info
From a LAN client e.g      I can ping both NICs on the XP machine    ie and but cannot ping
LVL 10

Expert Comment

ID: 24420919
The default gateways of the hosts on the LAN network should be the IP of the LAN nic of the PC you want to be the router..., I think it says. is another pc maybe?

The route table of the xp router box is probably fine, though It is not attached. It should have a default route pointing to the DSL Router, and connected routes to and, no command line tweaking necessary.

If you load wireshark on the gateway box you can watch traffic to see what is going on.

The LAN pcs should be using the default route to send all traffic destined for hosts not on their local network to the layer 2 MAC of your gateway PC.
LVL 10

Expert Comment

ID: 24420949
Did you change the IP of the gateway pc's LAN side NIC?

It looks like the PCs know about the gateway if they can ping both sides of the router pc, that is unless the gateway PC still has bridging enabled, which is going to confuse us a great deal.

Author Comment

ID: 24420970
The LAN NIC of the xp router is
I will try to attach again

Author Comment

ID: 24420992
Bridging has been removed unless there is something still lingering in there which has not been deleted properly
LVL 10

Accepted Solution

lanboyo earned 250 total points
ID: 24423693
If the inside interface is .254 then I see no indication that you are still bridging, the two areas of possibility are, the pc is not routing packets thru it, or the router isn't sending back to the 10 network.

If you can find a ping utility on th router, ping the pcs inside interpace.

While pinging a nonexistand device from an inside pc, do an arp -a command on the gateway pc .

It should arp for the non existant ip, and there should be an incomplete arp entry for it. Do not ping it from the gateway pc first. We want to see if it generates an arp entry on behalf of the inside pc.

Finally, download and install wireshark on the gateway pc.

Author Comment

ID: 24430527
Due to time constraints and a major shift in direction from work i will have to abandon this project and find an alternative however i would like to revisit it at a later date to try to solve this problem which would be interesting to find the solution.
Thanks for all the comments and help and i hope to get back to you within 2 weeks
I would like to leave this question open for a while to give the oportunity to allocate points when resolved

Once again many thanks

Author Closing Comment

ID: 31582339
Although you did not provide to exact solution i apprecaite your efforts to find the solution and they did help me pinpoint the problem area.
The problem was on the router. Unable to insert a static route to the local network. When I replaced the router with a PC and entered a staic route the problem was solved. Now I can deploy this situation in working situation with more confidence.
Many thanks for youe efforts

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