I messed up my network : (

Hiya, heres a noob question:

I have 2 pcs connected to each other, both using Windows XP.
Everything used to work until I formatted one of them.

Now, Im pretty sure the local area connection on the formatted computer isnt configured well - and all I get is a yellow warning "Limited or no connectivity".

Tried leaving it to Windows to decide on the IP address automatically, but it will just wait a minute or two before giving me that warning again.
I tried setting the IP up manually to what it used to be, no go.

So Im doing something wrong apparently, the question is what?
Thanks much.

So is this an internet problem? Are you using one computer as a gateway/hub to the internet and the 2nd computer isn't connecting propperly? Or is it just a plain comp-to-comp network?

Are both having problems, or just one, which one? Be a little more specific

Its just a plain network connection from the card in one computer to the card in the other one.
I do have an internet connection that I used to share when the network was working - the internet connection is fine.

So yes, both pcs cant communicate with each other and give me the above warning.

well when you formatted one computer you may have to re-install the network card drivers if XP didn't do so automatically. If you go into your control panel -> network settings on the formatted computer, does anything show up? if you have the drivers installed a "lan connection" should show up and you should be able to communicate with the other computer.

I've never gotten a limited or no connectivity on a wired network so I'm not sure.

The driver is installed correctly.
Local Area Connection is in the LAN section of Network Connections, along with Internet.
Both have their ethernet devices set.

Try to set both ethernet interfaces that connect the two pc's together on a subnet that is not used by the ethernet interface that is the default gateway ( your internet connection interface ).

For example take a class C addres:

Subnet mask: 255.255.255.252 ( you still have space for exactly 2 hosts, which is just enough in this case ).

PC1 ( the one that is connected to the internet ):

IP: 192.168.111.1
subnetmask: 255.255.255.252
default gateway: ip address of interface connected to internet

PC2 ( the one without internet connection)

IP: 192.168.111.2
subnet: 255.255.255.252
default gateway: 192.168.111.1

Now you should be able to browse onto PC1 from PC2, by typing into windows explorer "\\192.168.111.1" .

If that does not work, try to ping from PC1 to PC2, if that works then it has to be some upper layer problem but at least it won't be somewhere in the layer 3 ( or lower ) of the tcp/ip model.


note: do not use 192.168.111.0 or 192.168.111.3 as an ip for PC2 or PC1 since those are the network and broadcast address.

I dont have administrator privileges on the second computer (the one I did not format of course) and as far as I know it is set to acquire IP and subnet automatically.

Since it used to work with its current settings, there must be a way to only change the other coputers settings, isnt there?

edit: pinging from pc1 to pc2 will time out.

Quote:

---

Since it used to work with its current settings, there must be a way to only change the other coputers settings, isnt there?

---

There probably will be, but without more info on how the rest is configured all one can do is guess and hope he guesses right.

First things first, by checking that a PC should dynamically be assigned an IP you need a DHCP server, BOOTP or whatever it is that is assigning the addresses "dynamically".

In this case it will probably be the pc connected to the internet that is configured to hand out an IP address to the other pc over the ethernet interface connecting to the other pc.

If that is not the case with the pc connecting to the internet, then you should asign the other pc with an IP yourself. When you do this, it should be in the same network as the LAN interface of the pc that is connected to the internet , not the network address of the subnet ( the first available address in the subnet ) and not the last address available in the subnet ( the broadcast address of the subnet ).

The gateway address should then be configured to be the IP on the interface of the LAN of the pc that is connected to the internet ( it can not be the IP of the interface that is the internet connection ).

There are tons of things one can do to mess up a network and of course there are tons of possible problems when troubleshooting a network. ( this is one of the reasons why a network - as small as it seems - should be documented , unless the only person that is using the network is the one who did the design of it )

ps: I hope you tried ping 127.0.0.1 on the formatted pc already , just to check wether the tcp/ip stack on that pc is working.

>> In this case it will probably be the pc connected to the internet that is configured to hand out an IP address to the other pc over the ethernet interface connecting to the other pc.

This is indeed the case. Let me clear a bit:

This is how my settings were before I formatted:
PC1(the one I formatted) - Local Area Connection had an IP address and subnet mask set for it, I wrote them down.
PC2 - Has its IP address assigned automatically as far as I can tell.

After format:
PC1 - I tried to set its Local Area Connection IP to the one I put down.
PC2 - Unchanged.

I thought Im using common sense here, but apparently something is missing - it wont work.

>> I hope you tried ping 127.0.0.1 on the formatted pc already
The ping succeeds and the packets are received.

Yes PC2 will have the ethernet interface that connects to the internet probably dynamically assigned. But PC2 will also have another ethernet interface ( else it would be impossible to have another network :)).

That "other" interface, how is that one configured ? It can very well be that somehow that IP has changed, thus rendering the connection between the 2 pc's useless.

Just give the IP / subnet of that interface and the IP/subnet of the interface on PC1 ( the one you wrote down ).

You got it wrong I think.
The PC1 has two network cards - and is the one that connects to the internet.
PC1 is the one I formatted, and since PC2 hasnt changed a bit, PC1 is the one I assume I have to configure.

The settings that used to work on PC1 before I formatted it -
ip: 192.168.0.1
subnet: 255.255.255.0

on PC2, the ones acquired automatically-
ip: 169.254.35.149
subnet: 255.255.0.0

PC2 is the computer I have no administrator priveleges for

I dont have it wrong but again give specs about the wrong interface on the computer that is connected to the internet.

But alright lets give this a go:

PC1:

192.168.0.1
255.255.255.0
default gateway: 192.168.0.2

PC2 ( on the LAN interface , not the internet interface ):

192.168.0.2
255.255.255.0
default gateway: 169.254.35.149

PC2 Internet interface: leave this for what it is.

note:

since you dont have any admin privileges on PC2 you wont be able to change the ip address of the lan interface, therefore, make sure the default gateway of PC1 is the IP address of the LAN interface of PC2.

And yes , you shouldnt touch PC2, but when you enter a wrong default gateway at PC1 or place it in a different subnet it will get LAYER 2 connectivity of the OSI model ( based on mac addresses ) but you will not get any tcp/ip connectivity.

>> PC2 ( on the LAN interface , not the internet interface )

Im not sure I quite get you, is the IP I gave not the LAN interface?

>> since you dont have any admin privileges on PC2 you wont be able to change the ip address of the lan interface, therefore, make sure the default gateway of PC1 is the IP address of the LAN interface of PC2.

Assuming the PC2 IP I gave is in fact the LAN interface, I already did this but it wont work.

Quote:

---

Originally Posted by glo

Assuming the PC2 IP I gave is in fact the LAN interface, I already did this but it wont work.

---

That address you gave:

ip: 169.254.35.149
subnet: 255.255.0.0

Is a class B address, since you say it is dynamically assigned this will be the IP your ISP has dynamically assigned to you.

You know what, just dump the output of a ipconfig command on both pc's and we'll go from there :).

Sorry Im such a brick.
anyway PC1:

C:\>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : PC1
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter INTERNET:

*I cut down this section*

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8139 Family PCI Fast Ethe
rnet NIC
Physical Address. . . . . . . . . : 00-50-FC-B6-58-E0
Dhcp Enabled. . . . . . . . . . . : No
IP Address. . . . . . . . . . . . : 192.168.0.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 167.254.35.149

C:\>

PC2 will output:
IP: 169.254.35.149
subnet: 255.255.0.0
deafult gateway: nothing

PC1 ( the one you formatted should have ):

Ethernet adapter Local Area Connection:

IP Address. . . . . . . . . . . . : 169.254.35.148
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 167.254.35.149



The .148 can be anything from 1 to 254 except for 149.

I did exactly that,
with these settings enabled, not only the network will not work, my internet connection will not connect either.
Thanks very much though, Ill probably have the administrator come here sometime soon and see whats wrong.

Well then im pretty sure it has to be some windows specific thing.

I have tried the same here at home and I get the same error, as soon as I unplug PC2 I regain my internet connection on PC1. It has to be some kind of routing loop although with those settings that should never occur.

So the problem lies somewhere how windows xp handles two interfaces and tries to forward packets from one to another.

If you find the solution , can you either PM me or post it here, since im really curious as to what the problem is.

Sure, np

As far as I remember this is the second time this thing happens.
Last time the admin managed to fix it in just a few clicks.

So count on an answer hopefully soon.

edit:
Hah! got it sorted out just now:
I had to play a bit with patterns of enabling / disabling the sharing for the internet connection, rebooting, until it worked out somehow.
The settings are set to what they used to be before the format as mentioned earlier.

Im a windows / linux user and something like this should never happen. If all configuration settings of a layer 3 protocol ( and of course lower layers as well ) are correct layer 3 activity should be working, no matter what layers are on top of this layer ( and then I think of the presentation, application layer etc ).

Any upper layer should keep away from lower layers, unless its about passing data between them , but it should not be controlling these lower layers at all.

I am going to try and simulate the same scenario on linux just for fun ( latest Suse distro PC to some Ubuntu version PC ) and see what happens.