Here's how to do it: Solve network problems

When you have network problems, it's like looking for a needle in a haystack to find the cause. Much of what happens on a network is invisible and difficult for many to understand. This makes network problems more difficult to solve, but not if you work with these tools.

Tip 01: Network and Sharing Center

The tools Microsoft puts into Windows to check network configuration changes with each version of the operating system. They don't always get better at it. For example, we were quite happy with the Network and Sharing Center. You open it by right-clicking on the network connection icon in the notification area of ​​the Taskbar, then choose Network Center.

If you have Windows 7, you will see a map of the network and it will also be clear at a glance whether the connection to the internet is working or not. Unfortunately, in Windows 8 these parts are missing again and only some information can be found about the active networks. In both windows you will find the option Resolving problems that allows you to let Windows check the network configuration and network connection. However, this process only provides useful information in standard situations. Still, it's always a good first step.

Tip 01 The Network and Sharing Center in Windows 8 (foreground) has unfortunately not improved compared to Windows 7 (background).

Tip 02: Network adapter

Your own network configuration is essential for a good network connection. In order to solve problems in your network, it is important that you know how the network is structured and where you can adjust certain settings. We first look at the different network adapters. You do this in the Network Center to choose Change adapter settings. You will then see the different network adapters.

On most PCs you will see at least a LAN connection and a wireless network connection, it can also be more or less.

The LAN connection is the network adapter with which you can connect the computer to the network via a cable, the wireless network connection is the network adapter for a connection to a wireless network. You will already see a status for each adapter.

A red cross means that adapter is not connected. You will often see a message such as "Network cable not connected" or "Not connected". Right click on the connections and choose Status for an overview of the current configuration. click on Details for even more information.

Tip 02 The status overview of a network adapter provides useful information about the connection and configuration of a network adapter.

Tip 03: Network Configuration

Is there a problem in the configuration of a network adapter? Or do you need to change the configuration of a network adapter to solve a network problem? Then open it Network Center and click Change adapter settings. Then right-click on the adapter whose settings you want to change and choose Characteristics. The most important settings are those of the network protocol. That determines the IP configuration: the combination of IP address, subnet and default gateway. Select from the list Internet Protocol version 4 and click Characteristics.

If you want to access an unknown network, set both options to Automatically. If you want to make a specific configuration, choose Using the following IP address and below it enter the computer's IP address, subnet mask, and default gateway. Also specify the IP addresses of the DNS servers. Confirm with OK and Close.

Tip 03 Being able to adjust the network configuration is an important condition for solving network problems.

Tip 04: Commands

A helper that Microsoft fortunately still leaves untouched is the command prompt. You start this via Start / All Programs / Accessories / Command Prompt but the real network nerd types of course cmd in the search box of the start menu and press Enter. Then type the command in the command window ipconfig and press Enter. You will now see the IP configuration of the computer. Important of these are the IP address and default gateway.

A first essential network test is checking the connection to the default gateway, the router, the door to the next network, and the Internet. You check the connection to the default gateway with the command ping followed by the IP address of the default gateway. For example ping 192.168.1.254. You must then get an answer four times. If you do not receive an answer, you should first check the network connection of the computer with your own network.

Tip 04 "Request timed out" and "Desination host unreachable" are ping errors showing that the connection to the router is not working properly.

Tip 05: More commands

If you are checking the cables in a connection, it can quickly be useful to continuously check the connection with the default gateway. You can do this by entering the command ping followed by the router's IP address and then -t to type. For example ping 192.168.1.254 -t. The computer will now continue to send packets to the router and will give an answer or an error message each time. You stop the command with Ctrl+C.

Another advanced command is nslookup with which you can request which IP address belongs to the name of a website. For example nslookup www.google.com. If you now get an IP address back, you know that the DNS service on your network, which all computers use when surfing, is working. In addition, you can ping the IP address again to check the connection to the internet. With the command tracert followed by the IP address of a site on the Internet, you can finally check the route to that site. You will then see all intermediate stations in the way between your computer and that site, with your own default gateway being the first.

Tip 05 Request the IP address of a site with nslookup and then ping and trace it to test the connection.

The network shell

Netsh is a utility that you can launch within the Command Prompt. You can use it to get very specific information about the network configuration. It is especially useful also when troubleshooting a wireless network. For that it has a few nice commands that give much more information than Windows shows by default.

First, open Command Prompt via Start / All Programs / Accessories / Command Prompt. With the command netsh and then pressing Enter now switches to the 'network shell', the prompt in the window now also changes from the standard C:\ prompt to a netsh> prompt. With the command wlan show interfaces plus Enter you get an overview of the available wireless network adapters and with wlan show all plus Enter you get an overview of all available wireless networks. Very handy is that this last command directly shows the signal strength plus the supported network protocol, the security and the channel used for every wireless network.

With a question mark (?) followed by pressing Enter, you get an overview of all the other options. To exit the network shell, type the command bye followed by Enter.

The netsh command is especially useful in combination with wireless networks.

Tip 06: Monitor connection

The program WinMTR is a free utility to continuously monitor the connection to a site on the Internet. It performs a combination of ping and tracert and graphically displays the results. WinMTR is free to use and can be downloaded in a 32 and 64 bit version. Download the version of your choice.

Open the archive file (zip) and click Unpack everything. Then go to the correct folder and click on the file WinMTR.exe to start the program. Type now host the name or IP address of the site you want to check. For example, use google.com or its IP address if you want to monitor the connection to the internet. click on Start. To stop the action click on Stop, to exit the program on exit. The copy and export functions allow you to use the program's data in another program.

Tip 06 WinMTR provides a live image of the quality of a connection to a site on the Internet.

Tip 07: Query DNS

DNS stands for Domain Name System. It is the name of the system and also the network protocol that translates a site's name into an IP address. DNS also plays an important role in email. For every e-mail message you send, DNS determines to which IP address of the e-mail server the message should be sent. At the heart of the system are the Domain Name Servers that maintain large tables of website names and IP addresses.

When you ask such a server for a name, you get the IP address and vice versa. You can ask such a DNS server a question via the command nslookup that you use in the window of the Command Prompt. For example nslookup www.google.com (see also tip 5). But it is more extensive with the program DNSDataView.

Go to //tipsentrucs.link.idg.nl/dnsdv. click on Download DNSDataView and open the zip file. click on Unpack everything and then run DNSDataView.exe. Now type in the window at Domain List the names of the sites you want to research. click on OK. You will then see all relevant information for the requested domain names. Compare this with that of the nslookup. Sometimes there are differences that can lead to errors, especially with ftp. It is often the fault of the provider, which does not handle your request via nslookup (the way of the computer) correctly.

If nothing responds at all, turn the router off and on. The router is usually the DNS forwarder in the home network that forwards all DNS queries.

Tip 07 Really interested in how DNS works? On Wikipedia you will find a good explanation about the different types of records.

Tip 08: Network users

More and more devices are using the wireless network. Wireless also means invisible, because who is on the wireless network? Fing makes those users visible. Go to www.overlooksoft.com and click Download Now. Select your operating system (probably Windows). Download the program to the PC and then start the installation. Then start the Fing program via the shortcut in the start menu.

Fing doesn't have a nice graphical screen on Windows, it uses text commands in a command prompt. The program asks you a number of questions about what it should do.

If you don't know what to choose, press Enter for the standard answer. For example, choose d for Discovery, press Enter at the network, choose 1 for the number of rounds, N at the Domain Names, text as output format, t for table format, C for on-screen output and Y to run the command now. A little later you will neatly see all currently active users of the wireless network with IP address, MAC address and the type of device.

Tip 08 The Windows version of Fing is somewhat spartan but provides valuable information.

Tip 09: DHCP Reservations

In addition to the users of the wireless network, the users of the wired network can sometimes be difficult to find. Or vice versa: you get a response from a device when you ping, but you have no idea which device that is. The first thing you can do is log into the router.

Some routers themselves have a graphical overview of all users of the network. Another option is to view the DHCP server logging. The DHCP server runs on the router and gives all devices that register on the network an IP address. You can often see on the router which devices have been given an IP address. Open your browser and type the router's IP address in the address bar.

Log in with username and password. Then search for DHCP Reservations that often with the part Network or LAN sit. Open the section and you will see an overview of the devices that are currently active or have been active on the network a few days before and that have been given an IP address via DHCP. So not all of them are, but often most are.

Tip 09 The list of DHCP reservations does not show the current users but the most recent users of the network.

Tip 10: PortScan

The DHCP reservation list therefore does not show the current overview of the users of the network. Also, the important devices often do not use DHCP but have a fixed IP address. That sometimes makes it difficult to find a device on the network.

A program that can help is PortScan & Stuff. This program sniffs the network for devices, and does so in a smart way. More and more devices are set up in such a way that they no longer respond to a ping request, for example computers with a standard Windows firewall no longer do that. Those devices have to be traced in a different way. For example, by checking whether services are active on an IP address, whether there are shared folders or whether UPnP is active.

PortScan & Stuff looks at all of this. Go to //tipsentrucs.link.idg.nl/ports. click on Download portscan.zip and save the file to the PC. Some antivirus programs catch on with this site: they don't trust it. This is not due to malware, but because some functions of the program are also used by hackers, for example.

Tip 10 The PortScan & Stuff download site is not completely trusted by some antivirus programs.

Tip 11: Scan network

PortScan & Stuff requires no further installation. So you can also put it on a USB stick to examine another network (for example, if friends ask you for a solution to their problems).

Start the program by double clicking on PortScan.exe. The program has several tabs. The first is Scan Ports where you a Start IP Address and a End IP Address can specify. In addition, you can choose the scanning method, only by IP address via Scan-only IP Addresses or more extensively via Scan only common ports and Scan all ports.

Enter the first address of your home network's IP range as the start address and the last address as the end address. For example 192.168.0.1 to 192.168.0.255. Leave the check mark Check SMB Shares to check for shared folders as well. then click scan to run the scan. The list of devices will slowly fill up. You will see the hosts and for some devices you will also receive additional information such as a name, MAC address and type of device.

Through the tab Search Devices you can request even more data from each device, such as the versions of software and the model. Here you can also see whether folders are shared and whether a device can be accessed via the browser.

Tip 11 PortScan & Stuff finds almost all devices on the network because it also searches in other ways than just ping.

Networking Tools for the Mac

Also for Mac OS X, the operating system of Apple computers, there are network tools available to help solve network problems. For a general impression of the network, start the finder and then choose Go / Network. Through Programs in the left sideline of the Finder you can select the Terminal open where you put the commands ping, traceroute and nslookup finds. Ping always continues indefinitely on the Mac, abort is done with Ctrl+C. In the search box, type the word Network and you find Network Utility.

This provides graphical versions of the commands mentioned, as well as new ones such as Whois to find out who owns an IP address on the Internet, and port scan. With the latter you query the services that are open on a particular computer, by typing in the IP address or domain name and clicking port scan to click. NetSpot is a nice tool for analyzing wireless networks.

The free version of this program gives a nice overview of the wireless networks and the settings that are used. You will also see the signal strength displayed for each network.

Mac OS X's Network Utility provides a graphical shell for familiar network commands.

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