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Ping - Network Troubleshoot

How to troubleshoot a slow computer network?

Troubleshoot Network - Ping

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Your network is slow. What do you do to make it faster?
The answer is not simple and the reason for your slow network could be a lot of things. You have to take a step by step approach and isolate the bottleneck. Once you isolate the point of failure it is easier to find the problem.

Many times a packet sniffer will help you find the problem faster. A good free packet sniffer is Wireshark. Another packet sniffer is Microsoft Network Monitor.

Here is a list of Windows-based network tools that can help you troubleshoot almost any problem in a Computer Network:
Ping – a network utility to test if a computer is up and reachable or not. Ping uses the ICMP protocol to send echo requests.
Nmap – a port scanner. You need a port scanner to enumerate open ports and live IP addresses.
Tracert – a utility that traces the path of a network packet enumerating all of the routers that it passes through.
Wireshark – a packet sniffer.
Netstat – a utility that enumerates all the open ports on the local computer.
Ipconfig – a utility to list or modify the properties of a network adapter.
Netsh – a powerful Windows utility to modify various network properties. It is a scripting utility that basically controls every aspect of the Network on a Windows computer.
One of the cool usages of the netsh is to reset the TCP/IP stack to the defaults without the need to uninstall and reinstall the TCP/IP protocol as we needed with the older OSs.
Route – enables the view and manipulation of routing.
Nslookup – a name resolution utility. Very useful to check DNS servers and validity of name records.
Arp – a utility that allows you to get information about MAC address to IP address resolution.
Getmac – Provides the MAC address and lists associated network protocols for all network cards for a local or remote computer.
Getname – displays the computer name.
PathPing – Combines the functions of Traceroute and Ping, very powerful tool.
Net services commands – Performs a broad range of network tasks such as Network mapping, authentication, controls services, etc…

If you are not sure how to use these tools read the Help or from the command line, (all of these are command line tools), issue the command with the help option, for instance: “pathping /?”. This will give you a list of other valid options.  

This article is part of a five posts series regarding Network Troubleshooting.

  1. How to troubleshoot a slow computer network?
  2. Troubleshoot a Slow Network – The entire Network is Slow
  3. Troubleshoot a Slow Network – Slow Server
  4. Troubleshoot a Slow Computer Network – Only One Computer on the Network is Slow
  5. Troubleshoot a Slow Computer Network – Your Computer is Slow and Not the Network

Troubleshoot a Slow Computer Network – Your Computer is Slow and Not the Network

Slow Data Transfer is not Always caused by the Network

Slow data transfers are sometimes caused by a slow computer. Determine if the computer is the reason by comparing the transfer speed with a different computer connected on the same switch port. If the speed is the same, the problem is your network. If you get faster data transfers with a different computer then the problem is the computer.

A computer could be slow because of various reasons:

A bad network card. Troubleshoot: Swap the network card and test the data transfers afterwards.
The computer is outdated and it runs software that needs more resources. Troubleshoot: change the computer.
Slow hard-drive. The hard-drive will always be the computer’s bottle neck. It is the slowest part of a desktop computer. Old hard-disks are very often seen in new computers. Hard-disk fragmentation is a frequent reason for slow computers. Troubleshoot: Defragment often your hard-drive and reserve a 25% free space on the drive.
The computer might be infected with a virus or a Trojan. Troubleshoot: scan the computer for viruses. On a Windows machine run the command “netstat -a -b” to see what ports are being used and which program is using them. Use a network sniffer and monitor the network activity on the specific computer.
The transfer is intermittently slow, check what background processes are using the CPU, Memory, and hard-drives. Windows Vista can sometimes be a resources hog by allocating too many resources for background processes such as indexing and running the antispyware. Antivirus or other antimalware can consume a lot of the computers’ resources. Troubleshoot: Change the schedule for maintenance tasks to a time when you are not using the computer. Check what other programs are running in the background and configure accordingly. Some antivirus programs enable scanning the network drives by default.
A slow network printer. A slow network printer can be caused by the power save feature. If you use the printer very often you might consider turning off the power save.
A slow Network Attached Storage device. A slow NAS could be caused by improper SAMBA configuration or a disk power save feature. The power save feature is fairly easy to fix, just disable it if you find that you are using the drive very often. The SAMBA tune up is more difficult and usually it is complicated to have terminal access to the device itself. Many manufacturers do not allow direct access to the OS. SAMBA is a free implementation of Microsoft’s SMB protocol. SAMBA, SMB and CIFS offer file and print sharing services for Windows and Linux/Unix machines

This article is part of a five posts series regarding Network Troubleshooting.

Troubleshoot a Slow Computer Network – Only One Computer on the Network is Slow

Only One Computer on the Network is Slow

Client Computer Network Mask Wrongly Configured
Your network is a class C network, (net-mask 255.255.255.0), and your client computer has its IP address configuration on a class B network, (255.255.0.0). Change the network mask of the client to match the network configuration.

Poor network cards
Bad network cards or bad drivers are very often the reason for poor transfer rates. Test the transfer rate with a different network card.
An outdated computer can also slow down your network transfer.

Bad Network Configuration
DNS Configuration
can be the cause a of slow network connections.
Wrong DNS address in the IP configuration can slow your network dramatically. Your DNS client will try to connect to an inexistent or not working DNS server then give up and try your secondary DNS server. This translates in slowdowns and sometimes even DNS resolution errors.
Fix: Ping the DNS address or, even better, use nslookup and connect to both of your DNS servers to check if they work.

The TCP/IP protocol stack corrupted.

Sometimes no matter what you do you can’t fix the network and this is because the TCP/IP becomes corrupted. The only thing that fixes it is a reset. On older Operating Systems, such as Windows 98 and Windows NT, the fix was to uninstall and reinstall the whole TCP/IP suite of protocols.
Fix: issue the following command to reset it: netsh int ip reset c:\resetlog.txt.

More Than One Default Route
Advanced Lan SettingsA very common mistake is to assign more than on default route to the same computer. Do not confuse load balancing with multiple Default Gateways. You are configuring two network cards, and both of them have a default gateway. This configuration will not work. Usually, a Windows computer will warn you that this is not a good idea, but some users will choose to ignore the warning.
This is a typical problem for laptop users, they connect into the Lan environment and leave the wireless connection on. This will create a lot of problems for corporate users and even for home users.
In order for this type of configuration to work, special routing rules and IP configuration is needed. it is easier to turn the wireless of or have an adapter manager that will automatically do that for you based on your rules.
Advanced Tcp/IP Settings
On a Windows XP there is a way to assign priorities to network cards using a graphic interface. from the Network Connections applet in the Control Panel, click on the Advanced menu and choose Advanced Settings.
On the Advanced Settings window arrange the network cards according to the correct priority.
Another way to achieve this is to change the gateway’s metric for each of the network adapters on the computer. To do this, open the TCP/IP properties on each of the network addapters with a default gateway configured, and click on the Advanced button. On the Advanced TCP/IP Settings window, uncheck the Automatic Metric for the Default Gateway, and enter a value according to your network topology. The lower the metric, the higher the preference for a default route.

This article is part of a five posts series regarding Network Troubleshooting.

Troubleshoot a Slow Network – Slow Server

Slow Server

How do we know the server is slow and the problem is not elsewhere?
Make a file transfer between any two other computers on the network. Compare the measurements with the server’s transfer rates.
What are the reasons for a slow server?
There are many reasons for a slow server. The server is many times the bottle-neck of a network. Here are a few reasons for a slow server:
An average, or below average network card, (you need good quality network cards for a server).
Server Network Card Underutilized. Connect your server on the backbone or on 1GB switch ports to make use of the high speed network card. You probably want to limit all your clients to transfer at 100Mb so that there is no traffic discrimination. If your server and switches support higher transfer rates, (10GB ports), make sure you make use of it.
Slow disks. Poor hardware is many times the main reason. Improper configuration, such as choosing the wrong RAID type, or not using write caching can be another reason.
Too many clients on a server. If too many clients make requests to the same single server this could overload the server and it will perceived as a slow network by the users. Measure your server’s performance on load using the performance logs and alerts and the system monitor in Windows. Usually the performance is changing over the course of a day based on the number of users who access the server at the same time. Sometimes adding another network card would be sufficient. Enabling cache writing on the SCSI card can help a lot, (make sure you install a cache battery), adding a new SCSI card and additional disks to offload the existing ones could be of help. Sometimes adding another CPU can make a difference, (if you have free CPU slots). Memory is very often the most used method of upgrading, but most of the times it is not the needed solution. Use the performance logs and alerts and the system monitor and compare with the recommended thresholds to determine what your bottleneck is.
Slow server response, (packet sniffer to determine the handshake time), Adjust the server’s configuration to optimize the handshaking time; (this is a fairly advanced optimization task).

This article is part of a five posts series regarding Network Troubleshooting.

How to Run Network Cables?

The best time to run your cables for a Computer Network is at the construction/renovation time. At this time it is the easiest to run cables and drill all the passage holes. If the building is already done and it doesn’t need any renovation you can still run your cables.

Fishing and Running Network Cables

For a new building, it is wise to run the cables through designated conduits and to calibrate your conduit so additional cables can be added at a later time if needed. Plan junction boxes at each floor or major node.

For an old building, installing conduits might not be possible. In this case you need to tie your cables in a bunch and secure the bunch to walls, ceiling, etc… You need to use a fish tape to fish your cables in the wall cavity. You might need to use a stud finder to avoid obstructing framing. Adjust your outlet’s position accordingly. Very often the help of a second person is needed when fishing cables, especially when you fish the cables from ceiling to the outlet, behind the wall. In this case on person feeds the fish tape down, or up depending on the case, the other person tries to catch the fish tape with another fish tape or something similar. Once the fish tape is on the position, passed through the drywall hole, attach your cables to the fish tape using duct tape. Run a pull line as well, it will be very useful in the future, in the case you want to add additional cables or replace the defective ones.

Rules for running Network Cables
Make sure before drilling any holes into joists, that you follow the building codes.
Take care of the network cable integrity:

  • do not drop objects on the cables
  • do not step on the cables,
  • do over-bend or over-twist the network cable

When you pull your cable through holes do not pull too hard as this could stretch the cable and modify its electrical qualities. Using a pull-string will provide additional firmness.
Try to avoid electric cables and other electromagnetic sources.

Cable Length and Routes

On an Ethernet type network, typically, we use a star network topology. This means that all of the devices connect into a central point, which is usually a network switch. The network switch receives and distributes all the network packets to network devices.

You need to plan your network so that the longest path from any two network devices is less than 100m, (328ft). If this is not possible plan using additional repeaters or switches. Position your network room, to obtain the least cable lengths.  

Mnemonic – Network Cable Standards

Network Cable Standards

If you are crimping a lot of RJ45 patch-cords and you always forget the wire sequence, here is a Simple method to remember the wire sequence and colors.

I always use the same standard and by doing so I don’t have to check all the times what particular standard i used on a specific cable. I use the T568B standard because there is a mnemonic to remember the wires order. The order of the wires always alternates striped color with solid color. Then the order of colors is RGBB, (the mnemonic uses red for the orange pair, and the colors are red, green, blue, brown.) The trick is to remember the the blue pair is always in the middle, (pins 4 and 5). The mnemonic works for me even though is a little forced.

How to Make an Ethernet Patch-cord

Tools and supplies needed for a network patch cord:

  • Twisted pairs cable
  • Scissors or cutter pliers
  • RJ45 male connectors
  • Good quality Crimper
Ethernet Network Tools

Ethernet Network Tools

Utp Cable Stripp

Utp Cable Stripp

Start by stripping the pvc cover off the twisted pairs cable. Remove about 3inches (7cm).

Separate and untwist the wires. Arrange the wires in order using your favorite cabling standard. Use the same standard for both of your ends.

If you are redoing just one end make sure you are copying the other one, otherwise your patch cord will not work.
I always use the same standard so I don’t get confused when I am redoing cables. I use the T568B standard because there is a little trick to remember the wires order. See at th post Mnemonic for Network Cable pinout for a trick on how to remember the cable order.

Network Cable Standards

Network Cable Standards - Wires order

Straighten UTP Wires

Straighten UTP Wires

Straighten Wires

Straighten the wires, making sure you keep them in order. It is very easy to mix the wires after putting them in order.
If doing this feels painfully difficult, try to find RJ45 male connectors with guides for wires. The guides keep the wires in place and help you insert them into the connector. It is a real help for a beginner.
Cut the wires just a little longer than the RJ45 connector.
Cut UTP wires

Cut UTP wires

Insert Wires RJ45

Insert Wires RJ45

Insert the wires into the connector ensuring that you keep them in the correct order. To keep the wires straight push up a little against the upper side of the connector while you slide them. This procedure helps you keep the wires aligned while inserting them.
When you reach the end of the connector the exterior jacket will be outside of the connector. Make sure you push a little more so that the jacket gets inside. at the time of the crimping the plastic indentation on the connector gets pressed on the exterior jacket, conferring the patch-cord more rigidity and resistance. If the jacket doesn’t get into the RJ45, the wires will be loose inside the connector. This will cause the wires to move and loosen up the point of insertion.
Insert Wires RJ45

Insert Wires RJ45

Crimp UTP RJrj45

Crimp UTP RJrj45

Crimp the connector maintaining the wires and the cable jacket inside the connector.
Inspect the cable, verifying that the wires are in the correct order.
Inspect RJ45

Inspect RJ45

Compare Ends RJ45

Compare the Ends patch cable

Proceed to the other end and untwist the wires. Maintain the same wires order. Redo the same operations as above.

Compare the two ends. Make sure they are identical. If they are not your cable will most likely not work.
For a 100Mb network only two pairs are needed, the active wires are at the pins 1,2,3 and6. For a 1Gb network, all of the four pairs are needed.

Compare RJ45 Ends

Compare RJ45 Ends

Network Cable Tester

Network Cable Tester

Depending on the nature of your job you might need to use a cable tester. For a small network a simple continuity tester will be sufficient. The tester injects a signal on one end and it tests the signal at the other end.
If the cable is correctly crimped all of the LED’s will light up in order. The shield LED might not light up if your connectors are not a shielded.
For bigger networks you will need a more complex tester that can measure attenuation, cable length, and can even give you an overall result of the point to point capability. This type of testers can sum up the various aspects of a measurement and tell you if your segment qualifies for a CAT3 or CAT5 or CAT6 connection.

How to Build a Computer Network

If you own or manage two or more computers you need to connect your computers in a wired network to share Internet Connection and other services.
Here is a complete How To Build a Network.

Whether you are doing it at home or at your workplace, creating a computer network is not very difficult if you are a handy person and you have basic knowledge of computer networks. We will cover here most of the concepts you need to make your own LAN.
Computer Network
The series of articles will show you how to create a physical network and how to configure it to provide various services to your network users. We will focus on TCP/IP networks as this is the most common networking protocol.

Why Do You Need a Network?

You need a network if you need to share services for two or more computers.
Services that can be shared include: File sharing, sharing a network printer, Internet sharing, email services, Intranet, media broadcasting, etc…
In a home network, it is very common to share a printer and the Internet Connection.
In Business environment, the network becomes more complex and many more services will be needed to accommodate the use of many computers in a single network. Such services are DHCP – for automatic IP configuration, DNS – for name to IP resolution, corporate email, Proxy Server – for increased security on Internet, Intranet server – this is a private web server, VOIP phone system, etc…

What are the Limitations of My Network

You Ethernet cables are limited to 100m between any two active devices. If you need more than 100m between any two active devices such as computer and switch or computer to computer, you need to add a repeater or a hub, a switch will work as well, at each additional 100 meters, (or 333 ft.).
Depending on your materials and equipment, your network can run at 10Mb/s, 100Mb/s or 1Gigabit/s.
The most usual is to use Cat 5 or Cat 5e cables and connectors. A Cat 5 network can provide a speed up to 1000Mb/s.
If you need to connect at longer distances the more suitable solution are
Coaxial cable – up to 500M, speed 10Mb. You need special repeaters or hubs or special network cards.
The fiber optic – 10Km or more, speed up to 100Gb, depending on the equipment. It is the most expensive solution; the price though can be affordable for slower connections. For slower connections, most of the cost will consist on running the cable between the two points.
DSL is the cheap way to connect two remote offices if you have an available copper pair between the two offices.

What Do I Need to Make My own Network?

To make your own Ethernet Network you need the following equipment:
UTP/STP networking cable, RJ-45 connectors, Crimping tool, Punch down tool, Keystone Jacks, Wire stripper / Knife, Network Tester, Patch Panel, Network Switching device. The list includes also a stud finder, drywall saw, measuring tape, mounting plate, fish tape, ladder, and the usual tools such as screwdriver, drilling machine, hammer, etc…
Ample descriptions on the tools and materials are provided by following the links.

Computer Network Planning

The typical Ethernet Network has a star topology. That means that you have a central device, (network switch), that connects all of your network participants. This is important for your planning since you will have to run all of your cables to a central point. Make your measurements and place your central point in such manner that all of your cables are 100m or less. This includes the patch-cord as well.
If you have computers farther than 100m you will need to install a repeater. Alternatively you can use other types of connection, (coax, fiber optic, etc…), see the limitation paragraph.
When you run a cable consider the maximum amount of devices that can be stuffed into that office. It is a lot cheaper to run an extra cable or two per each office location than to run a single cable after the initial installation.
Install the keystones as close as possible to the actual location of the computer. Plan this thoroughly and pick the best location so that the patch-cord is out of the way.
Buy extra cable and extra connectors.
Use common paths for your cables whenever possible. If you run ten cables at once saves a lot of work and time.
Plan your cable route. Use ceiling whenever possible, it is the easiest path. Avoid running the cables near big electromagnetic sources.

Buying Computer Network Tools and Supplies

Do not buy cheap tools and materials. If you do, you will be penalized in different ways:
At the installation time you will get all sorts of problems trying to connect poor materials, cheap cable will be damaged more easily when manipulated, connectors will break easier.
In time the quality of the network will decrease if poor supplies and tools are used.
Overall experience and quality will be very poor if you get too cheap. If buying expensive tools is not justified, (a one time job), try to borrow good tools and don’t buy cheap ones.
Follow the links to learn what to look for when you are buying specific materials.
Now that you planned and bought all the Networking tools and supplies you can proceed to the Running the Cables for a Computer Network.