Freeze lan when another adapter is enabled

What is the default gateway when only one NIC is enabled and when both are enabled? route print will give you that info.

Should I assume you have ICS enabled on the network adapter connected to the Internet? Because you do need that in order to share the Internet connection w/ the laptop. Or else some other gateway solution.

Also, go to Network Connections->Advanced->Advanced Settings->Connections and make sure the network adapter connected to the Internet is listed FIRST. Reboot if necessary.

Finally, just get a wireless router! Even a dirt cheap $10-15 router is better than dealing w/ these types of problems. It provides better protection anyway.

Sorry guys, I was not here for some days.

I have checked the suggestions given by both of you. Firstly, ICS is enabled and the settings mentioned by eibgrad are found to be OK here.

Now for the route print, the default gateway changes if I enable 1 NIC or both. May be I did not configured it well.
So I am giving the details of NIC settings here.
Desktop which has the internet connection and shares it with laptop has 2 NICs, namely "Internet" and "Home". Laptop has only one NIC connected to "Home" at Desktop.

Settings :
INTERNET
IP - 192.168.120.77
Subnet mask -255.255.255.0
Default gateway - 192.168.120.1
preferred DNS - 192.168.30.1
alternate DNS - None

This connections are manually configured by my ISP, not assigned by DHCP. NetBios setting is set to default and TCP/IP filtering is desabled.
LMHOST Lookup is not enabled. No WINS, only primary and connection specific DNS suffixes are enabled, not the parent suffixes. (These settings are found in ADVANCED settings of TCP/IP property dialog box). File and printer sharing is disabled here for security reasons.


HOME
IP - 192.168.0.1 (required by ICS)
Subnet mask -255.255.255.0
Default gateway - 192.168.0.3 (laptop IP)
preferred DNS - None
alternate DNS - None

Advances settings are same, no DHCP, I configured it manually, there may be some errors. File and printer sharing is enabled.


Laptop NIC
IP - 192.168.0.3 (required by ICS)
Subnet mask -255.255.255.0
Default gateway - 192.168.0.1 (laptop IP)
preferred DNS - 192.168.30.1
alternate DNS - 192.168.120.1

Advances settings are same, no DHCP, I configured it manually, there may be some errors. File and printer sharing is enabled.

When route print is used with only "Internet" enabled, default gateway is 192.168.120.1, but when "Home" is enabled as well, then it changes to 192.168.0.3. I have checked the order of connections in Advanced settings in network connection window, "Internet" comes before "Home". So what is the problem here?

These are the settings. And another thing, in properties dialog box of "Internet", under ICS section at advanced tab, "Allow other network users to control or disable the shared network connection" - this is left unchecked, the other option is checked as usual. What should I do?



Thanks in advance.

Why are you configuring ICS manually? You should configure the desktop<--->laptop network to use DHCP and enable ICS, it will just work. As far as I can tell, there's no need for manual configuration.

The mistake I see is the desktop's HOME default gateway is set to 192.168.0.3. There’s no such IP address in this setup. It should actually be blank since that *is* the gateway for the desktop<--->laptop network (or at worst, 192.168.0.1). And normally Laptop NIC would be assigned 192.168.0.2 (although 192.168.0.3 would work, you now have a bizarre situation where the HOME network adapter (the gateway) is assigned the laptop’s IP as its gateway???). Also, the DNS server for Laptop NIC should probably be 192.168.0.1. Usually the gateway acts as a relay to the actual DNS servers on the WAN (INTERNET) side, or may just pass them through (not sure which ICS does).

But all of these problems stem from having not used DHCP. If using DHCP is inadequate for some reason (e.g., perhaps you need some other fine tuning), then start w/ DHCP, dump the TCP/IP configurations on the HOME and Laptop NIC to see what ICS did, and work from there.

Now I remember one thing. Several years ago when I had this same configuration working correctly, I had DHCP enabled.
Then I faced some problem, some times when the client and the host both booted at the same time, DHCP failed.
Being frustated I switched to manual configuration, may be that was done correctly at that time because everything was working fine.

Then I had to format and re-install windows and apparently, forgot how to configure it. Now I am trying to enable DHCP, but cannot do it.
In my Desktop <-> laptop connection, I selected automatic IP and DNS, so DHCP is enabled, right? But I am getting "Limited or no connectivity" error and cannot use even the file and printer sharing, let alone ICS.

Now how can I enable this? I have several concerns. Can anyone answer these? I am not actually a tech guy, so consider me as a novice.

My first question : I have file and printer sharing enabled on desktop <-> laptop connection which is actually my private network.
But this sharing is disabled for internet connection. My ISP has some problems so I can see others' shared files and they can see mine. Since I am sharing lots of private stuff between laptop and desktop I disabled sharing on Internet connection.
So I guess they can no longer see my files through LAN (I am not asking whether it is hack-proof or not, they can't see it through network places or workgroup). Now if I use ICS to share internet connection with laptop, which already has enabled file sharing, is there any chance that others can see my files through network places or workgroup?
I have enabled windows firewall, and kaspersky IS 2009, but this is not always enabled for massive slowing down of PC.

My second question : How can I enable file sharing for the connection "Internet" in such a way that everytime someone wants to get into my PC through LAN, it will ask for a username+password? I have enabled fast user switching and since it is a home PC, I don't want to use logon password. Also I won't mind if I need to use the password for my laptop<->desktop connection, if that is necessary.

My third question : A little bit off-topic. Is USB LAN adaptor works similarly as PCI LAN adapters? I mean does windows treat it as other LAN adaptors and connection rules are similar? I may need one, so I need to know what kind of complexity I may face later.

My final question : Actually I have already asked it. Some ABCD tips or some shortcut tutorial about enabling DHCP to use ICS with file and printer sharing between to PC's(desktop is the host, laptop client). Just a step-by-step process with minimal description will do.

Looking for your suggestion.