Networking troubleshooting for dummies

Top 10 Home Networking Problems and Mistakes
Tips for Troubleshooting Windows File and Printer Sharing

How to Find a MAC Address

• Windows 95 and newer: winipcfg
• Windows NT and newer: ipconfig /all
• Linux and some Unix: ifconfig -a
• Macintosh with Open Transport: TCP/IP Control Panel - Info or User Mode/Advanced
• Macintosh with MacTCP: TCP/IP Control Panel - Ethernet icon

Causes of Dropped Network Connections
Windows Server 2003 Networking TCP-IP AND WINS AND IPSec AND Print AND Firewall (pdf)
Step by Step Configuration of NAT PAT
Router/Public IP
Configuring a Second Router on a Static Network

Ping requests seem to be redirecting to my own IP

ping 192.168.1.1
Pinging 192.168.1.1 with 32 bytes of data:
Reply from 192.168.1.25: Destination host unreachable.
Reply from 192.168.1.25: Destination host unreachable.
Reply from 192.168.1.25: Destination host unreachable.
Reply from 192.168.1.25: Destination host unreachable.
Ping statistics for 192.168.1.1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)

The WiFi signal is fine, i get full bars, and have checked the exact strength with InSSIDer. The ethernet cable is also fine.

Did vista change the way ping responds?
ping 192.168.1.10
Pinging 192.168.1.10 with 32 bytes of data:
Reply from 192.168.1.106: Destination host unreachable.
...
Ping statistics for 192.168.1.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
ping 192.168.1.111
Pinging 192.168.1.111 with 32 bytes of data:
Reply from 192.168.1.106: Destination host unreachable.
...
Ping statistics for 192.168.1.111:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Sounds like routing issue.
Is the 192.168.1.106 the local computer? Or this post may help
Ping 192.168.1.101 but the response is 192.168.1.107

Reply from other computer destination

Ping problem - Spiceworks Community

Please tell me why I have different result when I ping from 2 workstation on my network. 

Pinging 192.168.137.101 with 32 bytes of data:
Reply from 192.168.137.199: Destination host unreachable.
[where 199 is the workstation(Windows 7) IP]

or
Pinging 192.168.137.101 with 32 bytes of data:

Request timed out.
...


Ping statistics for 192.168.137.101:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
[the IP of the workstation (Windows XP)is 192.168.137.29]
....

While I'm not sure the results are displayed differently. Both errors tell me that the device you are trying to ping is OFFLINE or the Firewall is enabled and ICMP is blocked. 

------------------

Is 199 the workstation you are trying to ping or 101 and 199 is the switch? (that is what it looks like to me)?
Are you pinging from two totally different machines to the same destination? If so it looks as if (guessing) you might have a bad network cable or switch port in regards to the destination machine.

----------------------

Are you pinging for the name or the ip address?
You could try to flush the DNS on both machines you are pinging from by entering in
ipconfig /flushdns 
at the command prompt to make sure they have the latest info from your dns server.

Or get into the dns server and

• remove the entries in both the forward and reverse lookups then 
• reload to make sure they match the ip address of the machines and then 
• flush the dns on the machines you are pinging from.

Run a tracert and see where it fails to know if it's a turned off switch in between or the end device that's unavailable.

-------------------

My take?
192.168.137.199 is your Win7 workstation.
The replies are from this adapter telling you it cannot "Find" the 192.168.137.101 IP Address
This is the Expected response in this situation from Win7
The XP machine gives its default response for a non responsive ping, request timed out. This also is the expected response from XP.
No problem, this is the proper response from both machines if they cannot get to the IP address requested.
The issue is:
Why can they not get to .101, possibly a firewall issue?
-------------------
Response indicated is correct for both a WIN 7 and XP OS. To troubleshoot ping your gateway to verify you are reaching your switch then ping .29 from 199 and the reverse that will prove that you can reach the switch and other machines on the same subnet. If that works check the .101 device for connectivity. Your options for 3 devices in the same subnet are incorrect gateway, incorrect subnet mask, software or hardware firewall blocking ICMP, no power or no lan connection at device .101.
-------------------

Do you have any kind of subnetting in place? If your Win7 box is 255.255.255.128 or smaller you will be spanning subnets and if you don't have routing in place, you'll receive that error.
For the XP side, check that .101 is online and has no FW running. Timeouts usually mean the machine is not there or is blocking ICMP.

-------------------

Win 7 is probably using IPv6 and your XP is not. You could also check your DNS on both machines, but I'd guess it's the IPv6 on Win7 causing your issue.

=======================

Unable to connect but could do previously

ipconfig /all 

DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.1.3(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : 03 July 2011 10:23:37
Lease Expires . . . . . . . . . . : 06 July 2011 10:51:57
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled

ping 208.67.222.222
Pinging 208.67.222.222 with 32 bytes of data:
Reply from 192.168.1.1: Destination host unreachable.
Reply from 192.168.1.1: Destination host unreachable.
Reply from 192.168.1.1: Destination host unreachable.
Reply from 192.168.1.1: Destination host unreachable.
Ping statistics for 208.67.222.222:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
 

This is very odd...

Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.1.1 ...
the reply IP is from another PC! 

Correct behavior:

ping 192.168.2.1
Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.2.1: bytes=32 time=3ms TTL=64
Reply from 192.168.2.1: bytes=32 time=2ms TTL=64
Reply from 192.168.2.1: bytes=32 time=4ms TTL=64
Reply from 192.168.2.1: bytes=32 time=6ms TTL=64

It seems a common problem with Windows 7 that one's internet can suddenly be unable to connect via the ethernet cable or over wireless when it had worked previously.

There are numerous solutions that have worked for others according to my research but unluckily for me none of them are resolving this issue on my system and I have been forced to seek guidance.
Compaq 615
Windows 7
TP-Link modem model: TD-W8901G
Everything worked great for the first week I had this service installed then I unplugged the modem to clean my room and haven't been able to connect since, either via wireless or with the cable despite the connection showing a strong signal.

I know some services from 3rd party software can create problems like mine, such as anti-virus bundles or Apple software but I don't have the usual culprits running, such as Bonjour routine/program that comes with Adobe CS3 or Mcafee anti virus.

Here are some things I have already tried...
Update the network driver.
Steps to update network driver:
1. Click on start button.
2. In the search box type devmgmt.msc and then press enter.
3. Select the network card device and right click on it
4. Now select properties.
5. In the properties window, under Driver tab, click on Update Driver button.
6. After the installing the updates restart the computer.
For more information visit: Update a driver for hardware that isn't working properly
Tried this, it didn't work.

Try resetting the TCP/IP stack.
To reset the TCP/IP stack go to this article and either click on "Fix it for me" or follow the instructions to fix it yourself: How to reset Internet Protocol (TCP/IP) .
Tried this, it didn't work.

Troubleshoot using the Network troubleshooter in Windows 7 and check for the issue. Follow the below provided link.
Using the Network troubleshooter in Windows 7
Tried this, result was:
"Your broadband modem is experiencing connectivity problems.
Restart your broadband modem:
1. Unplug or turn off the modem.
2. After all the lights on the modem are off, wait at least 10 seconds.
3. Turn the modem back on or plug it back into the power outlet.
To restart a modem that has a built-in battery, press and quickly release the Reset button. If this doesn't fix the problem contact your internet service provider.
Problems found
The connection between your access point, router, or cable modem and the Internet is broken."
I followed those instructions and nothing worked. Despite it saying I have connectivity problems, remember it does show a strong signal!

Uninstall and reinstall ethernet adapter driver.
Tried this, it didn't work.

I first learned that by disabling and then enabling the local area connection, internet access is restored. Certainly its not the perfect solution and i can bare myself the pain in doing the same task every time i turn the PC on.
Fix No Internet Access in Windows 7 - Tildemark blogs
Tried this, it didn't work.

Disable TCP-IPv6
Tried this, it didn't work.

Go to Start - Search Box - TYPE "msconfig" - Hit Enter - Services Tab - Click the ceck next to ##Id_String1.6844f930_1628_4223_b5cc_5bb94b879762## Apple Computer, INC - Hit OK and Restart your computer.
Tried this, I don't have this Id string listed.
 

1. Take the LAN cable out
2. Restart and allow the WiFi to function or find nothing
3. Plug the LAN cable in. From this point on (until the next time you Restart), no "Unidentified Network" (two conflicting Networks) and Internet Access.
Tried this, it didn't work.

Unplug router for a minute, or reset it.
Tried both, neither worked.

Router firmware upgrade will solve problem working with windows 7.
Tried this, but was unable to follow the process because I get a dialogue box pop-up requesting user/pass:
"A user name and password are being requested by http://xxx.xxx.xxx.xxx. The site says: "TD-W8901G"
With both the correct username and pass (pasted from network properties) or original password (given that I had changed it) for some bizarre reason it doesn't seem to be accepted. Definately and unconditionally the correct user/pass but not accepted and thus cannot attempt possible firmware upgrade solution.
Turn firewall off.
Tried this, it didn't work.

Find and select "Internet Protocol Version 4 (TCP/IPv4) in the list then choose the properties button.
The properties window for the TCP/IPv4 protocol opens.
I have the buttons for "Obtain an IP address automatically" and "Obtain DNS server address automatically" selected.
Click the "Advanced" button to open up the Advance TCP/IP Settings window. It should show that you have DHCP enabled, however, in my case the default gateway address for my network was blank. I clicked the "Add" button beneath the Default Gateways box and added the gateway setting for my LAN here. That was it. As soon as I clicked the add button to add the gateway IP address I entered, it connected and I had full Internet access and no further problems connecting automatically after rebooting Win 7.
If you don't already know your LAN's gateway IP address, you can find it by going to the "Search programs and files" box on the Windows Start Menu (bottom left) and typing the command "cmd". Then hit enter to bring open a DOS box. In the DOS box window type the command "ipconfig" and hit enter on your keyboard. Look at the resulting list of numbers displayed beneath the section titled "Ethernet adapter Local Area Connection." The IP address of your LAN's Gateway is listed across from "Default Gateway."
Tried this, it didn't work.

Safe Mode With Networking.
Tried this, it didn't work.

Start
Accessories
Scroll to the "Command Prompt"
Highlight "Command Prompt"
Hold Shift and Right-click on "Command Prompt"
Choose "Run as Administrator"
You are now in the System32
Run this command: netsh winsock reset
It will prompt you to reboot your pc.
Reboot and try to reconnect to your preferred wireless.
Tried this, it didn't work.

Go to the device manager
select network card
right hand mouse button and go to properties
then the advanced tab
find network address
select not present
Now go to start and type CMD at the prompt type:
ipconfig /release
Enter
ipconfig /renew
Enter
Tried this, it didn't work.

 
- Click Start Button
- Type: ncpa.cpl
- Right click the Wireless Adapter and choose PROPERTIES
- Click and highlight the Internet Protocol TCP/IP Version 4 option
- Click the Properties button
- Choose “Use the following IP address”
- Enter the following for the IP address: 192.168.1.210
- Enter the following for the Subnet Mask: 255.255.255.0
- Enter the following for the Default Gateway: 192.168.1.1
- Choose “Use the following DNS servers”
- Enter the following for the Primary DNS server: 192.168.1.1
- Enter the following for the Secondary DNS server: 4.2.2.3
- Click OK
- Click OK
- Reconnect to the wireless signal
Tried this, it didn't work.

 ----------------------------

Have you tried a direct connection to the Modem, bypassing the Router?
Post an ipconfig /all of the computer in question for review.
Click on Start => in run or search box type cmd press enter (run as Admin for Vista and 7). From the black screen, type the word ipconfig /all and press enter. Right click on the black screen or Command prompt then choose Select All and Paste the results onto your Post. 

------------

Have you confirmed that none of your browsers are using Proxy servers?
No but I get the yellow exclamation mark on my connection on the taskbar so it seems to be the whole connection rather than just via Firefox and IE.

------------

Ping DNS

Not sure what this is or how to do it but I tried C:\WINDOWS\SYSTEM32>nslookup and got this:
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Windows\system32>nslookup
DNS request timed out.
timeout was 2 seconds.
Default Server: UnKnown
Address: 192.168.1.1

-----------------

Let's try assigning Static IP to both your LAN and Wireless config by following this guide:
Setting a Static IP Address in Windows 7 - PortForward.com
For your Wireless Setting assign the following Static IP:
IP Address - 192.168.2.51. If this IP is already taken try assigning a diff IP as long as it won't past 250.
Subnet Mask - 255.255.255.0
Gateway - 192.168.2.1
DNS - 208.67.222.222
For your wired connection assign these Static IP:
IP Address - 192.168.1.3
Subnet Mask - 255.255.255.0
Gateway - 192.168.1.1
DNS - 8.8.8.8 and 8.8.4.4
Also, if you want to use your wired connection, disable your wireless connection, do the same method to your wireless connection to avoid conflict, see if it works this time.

One pop-up:
Warning: Multiple default gateways are intended to provide redundancy to a single network (such as intranet or the Internet).
They will not function properly when the gateways are on two separate, disjointed networks (such as one on your intranet and one on the Internet). Do you want to save this configuration? Yes/No
I figured the new settings for the problem wireless connection are conflicting with the wireless from the school so I disabled that adapter but it hasn't stopped the pop-up warnings. Here is another one:
The IP address 192.168.2.51 you have entered for this network adapter is already assigned to another adapter 'Miscrosoft Virtual WiFi Miniport Adapter' on this computer. If the same address is assigned to both adapters and they both become active, only one of them will use this address. This may result in incorrect system configuration.
Do you want to fix the problem by entering a different IP address for this adapter in the list of IP addresses in the Advanced dialogue box? Yes/No
-------------------- 

Please switch the settings back to the way they used to be, DHCP or auto IP assignment on both LAN and Wireless.
Do these commands on both. Click on Start and type cmd.
From Command prompt screen type:
ipconfig /release press enter
ipconfig /renew press enter
Now, disable your wireless connection, then try to connect using your wired connection.

------------------------

It won't release and renew with out proper IP's assigned.
Lets Power Cycle your Modem and your computer to get the IP back.
You may do another ipconfig to see if IPs are back. Test your wired connection after.
How to Power Cycle Your Computer and Internet Connection. | Schrock Innovations Computer Company

---------------------

Is your Network Adapter disabled? Your ipconfig shows a Media Disconnected.
Also, you'll have to type ipconfig /all next time to show us the entire output.
At this point you might want to contact your ISP again and be very persistent. There might be something wrong with the modem.
Can you give us a print screen of your computer's Device Manager, expand Network Adapters?

---------------------

REALLY STUPID..!
These problems all started when I disconnected and unplugged the modem so I could give the room a good clean. One thing I hadn't tried was connecting a cable into a little box with a picture of a telephone on it. I thought this was simply for a landline but given my options had more or less run out I gave it a whirl and hey presto my internet is back! 

-------------------------

Okay... you might have overlooked the RJ11 or telephone port

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http://www.eggheadcafe.com/searchform.aspx?search=dhcp+both+servers

Linksys WRT54G as a wireless ethernet bridge

forums.anandtech.com/showthread.php?t=1115
network-technologies.org/Projects/Virtual_Brain_Online.php/article/62/