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Posts Tagged networking

Tanvir's laptop NIC issue

Aug 13

Posted by Mike in Technical Journal | No Comments

Spent a long time troubleshooting Tanvir Suri’s laptop issue.  He would go to a hotel and be able to connect via wired connection without an issue.  Then he would get back into the office and would be unable to connect.  He would get “limited or no connectivity available” in the bottom right corner.

I went through a lot of stuff to troubleshoot.  Wireshark packet captures.  DHCP discover packets were being created, but nothing being received back from server.  It kept falling back on the APIPA (Automatic Private IP Addressing).

Laptop was connected through a cisco phone switch (pc port on phone) so to eliminate possible problem with the phone we disconnected cable from back of phone and had him connect directly to laptop.  No change.  Assigned static IP address provided by Marc Robinson.  Still not pingable and unable to ping out.

I had already done the winsock reset netsh winsock reset catalog and the TCP/IP stack reset netsh int ip reset reset.log and still wasn’t working. Finally I just uninstalled the network adapter and reinstalled and that solved the issue. Ended up being corrupted network driver. I did have an issue when removing it as it gave the error “Failed to uninstall the device. The device may be required to boot up the computer” but I followed the steps I posted here in my other blog entry.  Then all was good.

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Failed to uninstall the device

Aug 13

Posted by Mike in Technical Journal, Technology Recipes | No Comments

“Failed to uninstall the device. The device may be required to boot up the computer”

This happened to me today on an Acronis restored Small Business Server box (to different hardware using universal restore).

The issue is that the HP server that the image came from had HP drivers that ended up blocking the broadcom drivers on the Dell server I was moving to. The way to fix the issue is as follows:

1. Go into a command prompt.

2. type “set devmgr_show_nonpresent_devices=1”

3. Hit return.

4. Type “devmgmt.msc”

5. Hit return.

Once device manager has loaded, go to View, Show Hidden Devices.

You will then see “greyed out” old devices and network cards that you can remove.

Once you reboot all should be well.

via “Failed to uninstall the device. The device may be required to boot up the computer” – Nick Whittome – The Naked MVP.

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TCP/IP, DHCP, Routing Good Conversation

Aug 13

Posted by Mike in Technical Journal, Technology Recipes | No Comments

>> The routes look good to me too.
>> Your wired connection has priority over the wireless, so I assume
>> that you unplug your wired connection when testing the wireless.
>> — John>

No, all I’ve done is try to establish an incoming connection by> pinging 10.0.0.204, or trying to connect a VNC client to that> address. I’ve checked the machine’s firewall, and set specific> permissions per adapter, no joy.When a ping packet comes into the wireless address 10.0.0.204, thecomputer tries to send the ping back. According to the routingtable, the wired connection 10.0.0.138 has priorty on outgoingpackets to the 10.0.0.x subnet metric 20 vs. 40, so the return pinggoes out the 10.0.0.138 port. When the return ping arrives at thesending computer with an origin of 10.0.0.138 instead of 10.0.0.204,it discards it because it came from the wrong device and you don’tsee a response.A similar thing will happen on all incoming connections to yourwireless adapter… The return packets will exit on the wired portand confuse the sending device.If you physically unplug the wired connection, then the wirelessconnection will become the priority connection and things may startworking.HTH, John

> John Wunderlich wrote:
>> Philip Herlihy <thiswillbounceb…@you.com> wrote in
>> news:QMrVl.14$Hj6.12@newsfe09.ams2:
>>> It seems very surprising that Ping works this way – this won’t be
>>> the only machine out there with more than one network adapter!

>> It’s not “ping” that works this way, it’s the Network Stack that sits
>> between the NICs and the Applications (e.g. ping) that receive and
>> send packets.  An application will generate a data packet and send it
>> to the network stack which will take care of adding TCP and Ethernet
>> headers, checksums, etc, before directing it to the appropriate NIC to
>> send to the network.

>> You’re right.  Lots of machines have more than one network adapter.
>> The catch in your case is that both adapters connect to the same
>> subnet.  The norm is to have one NIC connecting to one subnet and the
>> other NIC connected to a different, perhaps small, local subnet.  Just
>> Google for “multiple nics same subnet” and you will see the problems
>> that people have.

>> — John

> Quite an education!

> Thanks, John!

> Phil

Most definitely an education.  Once I got the user to disconnect the
Ethernet cable, the connection worked: I can ping the adapter and she
can browse the web – all wireless.
So, one of my tweaks must have fixed things, but since I was operating
remotely via cable, that was obscuring the results.  I guess if I wanted
to try this again I’d set up a (non-persistent) route through the
wireless adapter using “Route Add” for just one target address, and
fiddle around until I could connect to that.

Thank you for your patient and invaluable help.

Best wishes,
Phil (happy now)

> I guess if I wanted to try this again I’d set up a
> (non-persistent) route through the wireless adapter using “Route
> Add” for just one target address, and fiddle around until I could
> connect to that.

“Route Add” should work.  Alternatively, you could also change the
default metric for the wireless interface to have higher priority
(lower metric) than the wired connection — with different side-
effects, of course.

> Thank you for your patient and invaluable help.
> Best wishes,
> Phil (happy now)

Glad to help. Thanks for the feedback.

via Using Wireshark to troubleshoot wireless connections? – comp.os.ms-windows.networking.tcp-ip | Google Groups.

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Samba->SSH->Putty

Feb 27

Posted by Mike in Technology Recipes | No Comments

Install a loopback network adapter

A loopback network adapter is kind of a “virtual network adapter”: it acts as a normal network adapter, but you don’t have to install any physical hardware to use it. It is only usable on the PC it’s installed on (other PCs can’t connect to it).

  1. Go to Control Panel – Add Hardware
  2. Click Next, then wait a while, choose “Yes, I have already connected to the hardware” and Next again.
  3. Choose the last option, “Add a new hardware device”, click Next.
  4. Choose “Install the hardware that I manually select from a list (Advanced)”, click Next.
  5. Choose “Network adapters”, click Next.
  6. Choose Microsoft, “Microsoft Loopback Adapter”, click Next and Next again.
  7. Click Finish.

Configure the Microsoft Loopback Adapter

Since the loopback adapter won’t have a DHCP server to ask for an IP address, we need to configure an IP address manually.

  1. Right click on “My Network Places” (on your desktop or in your Start Menu), click Properties.
  2. Find the network connection that is associated with the “Microsoft Loopback Adapter”. Usually it’s called “Local Area Connection 2″. For clarity, I renamed mine to “Loopback” (what’s in a name?). Right click the connection name, click Rename and change it.
  3. Right click the Loopback connection, click Properties.
  4. On the General tab: disable “Client for Microsoft Networks” and “File and Printer Sharing for Microsoft Networks” (only untick the checkboxes, DO NOT uninstall!).
  5. Click “Internet Protocol (TCP/IP)” and click Properties.
  6. On the General tab: click “Use the following IP address” and pick a private IP address on an unused subnet (I used 192.168.100.100 with subnet mask 255.255.255.0).
  7. Click Advanced.
  8. On the WINS tab: click “Disable NetBIOS over TCP/IP”, then click OK and again OK.
  9. Click Close.

Create or edit the LMHOSTS file

  1. Open the file “C:\WINDOWS\system32\drivers\etc\lmhosts” (create it if it doesn’t exist – note that the file should have no file extension).
  2. Add the following line to the end of the file:
    192.168.100.100 servernamehere
  3. Save and close.

Configure PuTTY

At last, we have to tell PuTTY to create an SSH tunnel from the loopback connection to our home server. I assume you already have a PuTTY saved session to connect to your home server.

  1. Open PuTTY, click your saved session and click Load.
  2. Go to Connection – SSH – Tunnels.
  3. In Source port, type “192.168.100.100:139″ (I know, the field is quite small, but it will accept the value anyway).
  4. In Destination, type “localhost:139″.
  5. Click Add, and do not forget to resave your saved connection!

To confirm that everything is working, connect to your home server with the saved session in PuTTY. Click Start – Run and enter “\\servernamehere\sharenamehere”. Depending on your Samba setup, you may have to enter a username and password. Done!

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