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Troubleshoot a Slow Network – The entire Network is Slow

The Entire Network is Slow

If the entire network or a part of the network is slow, this could be a strong suggestion for a faulty switch or a miss-configuration.

Poor network equipment
Usage of hubs is not recommended, (hubs are prone to collisions by design)
Cheap switches that cannot handle the total needed bandwidth. The switch’s chip can handle 100Mb/s for 12 ports, but the switch has 24 ports and all are connected. For low network usage this is not a problem, but if your network usage spikes, your switch will not be able to handle the bandwidth. The quick fix in such situation is to power off the switch for a few minutes and then power it back on.

A loopback is a network cable that has both ends connected to the same switch. If it’s a managed switch activating loop protection on all the ports could fix the problem. You can look on the switch’s log file for excessive broadcasts and isolate the two ports that are in loop. If you don’t have managed switches you can use a packet sniffer to determine if there’s a loop. A wrongly configured Spanning tree could cause a loopback.
FIX: Check all the patch-cord connections in the faulty switch. Check for patch-cords that have both ens into the same switch. Check for more than one patch-cord connecting the same two switches.
If you have cascaded switches it is normal to be slower for the devices in the cascaded switch but is not normal for the devices that are not cascaded. Check if any cascaded device is not connected on two ports on the wall, (usually the ports on the wall go to the network room). Your cascaded switch makes a loop into the upper level switch.

Bad Network Configuration
DNS issues
can cause a lot of slowdowns.
One common error is to use your ISP’s DNS server inside your Active Directory network. Your Active Directory computer members will try to resolve internal names by querying your ISP’s DNS. Those records don’t exist outside of your network.
Fix: For all of your Active Directory network clients remove any entries for your ISP’s and use only internal DNS servers. Configure your ISP’s DNS server as a forwarder on your AD DNS servers.

Network switching equipment wrongly connected is the reason of slow network for many small networks. Typically this happens when a small switch is connected to the router. When the switch becomes too small for a growing network, the first impulse is to connect the computers into the router directly.
: Install a switch that will accommodate all of the computers in the network. Disconnect any computers connected directly into the router.
Note: It is normal for the wireless connected computers to have slower transfer rate than the wired ones. Most of the wireless routers and adapters function at 54Mb per second. If your router is a modern router, (100 Mb or faster), and you still don’t get the expected transfer rates, you should revise your configuration as above.

Broadcast storm
You can efficiently detect a broadcast storm using a packet sniffer or a managed switch. With a packet sniffer you need to look for large numbers of broadcast/multicast (more than 20% of the total traffic it is an alarm signal). Locate the retransmission packets and search for the source MAC address. Disconnect the problem host.
If you suspect a broadcast storm in your network and you don’t have a managed switch or a packet sniffer, you can run download and upload tests by systematically disconnecting all of your computers in the network one by one. This is only practical in small network environment.

Virus Attack
A lot of connections originating from the same MAC address, to the same destination port, but for different destination address, and in short intervals.
Fix: Determine the source address of these connections and disconnect the suspect hosts. Run an antivirus scan on the computer before plugging it back. There are a few ways to determine the source of a virus. Use a packet sniffer, look on your managed switch for the ports with the most traffic and confirm it on the suspected computer by issuing the command “netstat -a -b”, (on a Windows machine). The command will show you which ports are active and which program, (executable), is using the ports.

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

How to Troubleshoot Internet Connection Speed

Who didn’t have problems with the Internet speed at least once? OK, many of us, but as an IT professional I always meet and talk to the people who did have problems with their Internet Speed.
I hate to be run through standard procedure, which by the way I know by hearth, (I used to work in an ISP call center). You probably hate it too. If your problem is the Internet connection you will probably have to talk to an agent anyway, but, (with the help of my article), you will know from the start what’s wrong with your Internet connection.

Step 0 – Never Assume

First think I have learned in the Call Center was to never assume. Many times, when people call the Help Line they have a “pretty good idea” of what’s the problem. Usually they are wrong. Don’t do this mistake, do not presume or, do not presume without checking the facts. We hate the Call centers for making us do stupid things, check things that we don’t need to. The truth is that in most of the cases we overlook things and going by the book helps.
When we open up a browser and there is an error message “Page not found” we immediately assume that the connection is to blame. In fact many times this is just a temporary problem of our home page site. Try a different address to see if the connections is down or the home pages’s website is down. Try google.com for instance or ibm.com, or bing.com; if these don’t work it could be the connection

Step 1 – Try a reboot

Almost every time a reboot solves the problem. This might sound anecdotic but it actually works in many cases. Reboot the computer, reboot the modem, reboot the router behind the modem.

Isolate the problem
First of all we need to know that the problem is not in the network.

  • Use a computer that you are sure is not infected by any Mallware. Connect it directly to the DSL device, cable modem, or other type of modem.
  • Do not use the wireless; connect the computer with a network cable. This way you are testing the connection and nothing else.
  • As already mentioned, you need to make sure your computer works fine and is not infected. Use antivirus and antispyware if needed.
  • If you are not sure about the health of your computer you can always boot from a Live Linux CD. On the Live CD you will have a browser and other useful tools.
  • Once the system is up and you are connected to the Internet, test your connection with one of the free online services. Google-it and you will find many online DSL speed test websites. If the speed is OK then, the problem is in your computer, or your network, go to step 4.
  • Step 2 – Modem troubleshoot

    If the DSL speed test failed, (no connection or slow speed), you have a few things to try before calling the ISP
    Usually, for a DSL connection, the telephone line is shared with another device, a fax or a phone. Some of us have a separate line for DSL or they don’t even have a phone line, they only have a dry loop. If you don’t understand any of these you most likely don’t have it.

  • If you share the DSL line with another device you need to connect this second device through a DSL filter. I must stress: EVEN IF IT WORKED before without it, you must have the filter.
    DO NOT run the DSL line through a filter, you’ll only break your Internet Connection, only the phone or the fax, or Credit Card processing device, etc…
  • Check all the physical connections of the Modem Device, R6 or RJ11 or the RJ45 connectors and make sure that they are tight they don’t have the locking pins broken, etc…
  • For a DSL connection the length of the phone cable could be critical, so use the original cable, (the short one), provided with the modem at least for the testing period. The reason is because the length of the pair from the CO to your place can be at its length limits, it happens more often than you think. If you pass this limit your connection stability will be penalized. Another reason is because a long cable is more difficult to examine for defects than a short one.
    If needed, use a longer network cable to connect a device in the house. The network cable, (UTP – unshielded twisted pair), can go up to 100m (300 feet).
  • Some electric devices can interfere with the modem; avoid placing it near such devices.
  • Look at the modem’s lights. If the DSL light is off there is no service.
  • If there is no connection at all, (No DSL light), check the phone to see if you have a dial tone.
  • If the modem connects to a separate wall jack bring a phone and check if you have a dial tone, you might have a dial tone in the bedroom and not in the office.
  • Similarly check if there is TV service, if there is no TV service then most likely it is a bigger problem at your cable provider.
  • Look for the DSL filter as described above.
  • Check the LAN light on the modem. If the LAN LED is off your computer’s network adapter might be defective, or disabled, or the UTP cable that connects the computer with the modem might be defective. There is a chance that the modem’s LAN interface is defective.
  • If you have a solid DSL light, (check the modem’s manual, manufacturers have different signalling for established DSL connection), and you don’t have a connection check the password for the connection.
  • Step 3 – Connect to Your Modem’s Administration Interface

    All of the modern modems have a WEB Administration Interface. The admin Interface is usually accessible via a WEB browser. It lets you configure the authentication and other different settings.
    In order to administrate your modem you need the following:

  • The administrator’s password to access your router. If you don’t have it you can perform a hardware reset using the reset button located on the modem. You need to use a pin to press the button. This will reset all of your modem’s setting, including the admin password, to the factory defaults.
  • The IP address of the router. If the modem has its DHCP server started, (by default yes), it will lease your computer an IP address and provide it with other IP configuration settings such as: “Default Gateway”, netmask, and DNS. The important part is the gateway’s IP address as this is your modem’s internal interface and this is what you need to access your router’s web Interface. You can find all of this information by issuing the following command in a command prompt window with elevated rights, (admin credentials):
    ipconfig /all
    After issuing the command you will get a screen similar to this one. Note that the “Default Gateway” is the address of your modem.
    In a web browser type: http://IPADDRESS where IPADDRES is your router.
    For instance if your router’s (gateway) IP address is the address you are looking for is:
  • Once connected to the web interface you need to enter the authentication details. If you don’t have them you have to call your ISP which will make a reset after security verification.
  • If all of the previous steps did not solve the problem call your ISP. They might ask you to redo all of the steps above and maybe more. Be patient, they are just doing their job, they never assume, or they shouldn’t. The second they let themselves drawn into your speculation they make the same mistake as you do.

    Step 4 – Correct the problems behind the modem

    If the connection is OK the problem is behind the modem. This problem could be anything in your network.
    Some suggestions are:
    The router – many times the router can slow down your network. Try a reboot. If that doesn’t work try another model or another manufacturer. Do an upgrade of the firmware. Check the router’s configuration and try a default stripped down configuration.
    The computer – most of the times, the slow performance over Internet is actually the poor performance of a computer. This is a dense material that is treated in a separate article which you can find here: How to Refresh your Computer speed (coming soon).
    The network – many times a poor network will penalize al sorts of network traffic not only Internet. This makes the subject of another article here: How to Troubleshoot Your LAN, (Local Area Network). (coming soon)

    Ask me any technical question in the comments area so I can update the document or answer you directly on the comments. I would like to make this article as useful as possible.

    Free Protection against Computer Viruses and Other Malware

    Today’s computers are under a constant assault of viruses and other malware. We all need to have up to date Antimalware software to protect our computer. Buying antivirus software and subscription could be expensive because you need to update your subscription yearly. However there are free options for your computer’s security.

    What is Malware?

    Computer Malware

    Malware is a general term for any software designed with the intention to affect negatively a computer or to steal private information.
    Malware includes computer viruses, worms, trojan horses, rootkits, spyware, adware, crimeware and other malicious software.

    There is a misconception that only Windows operating systems are affected by Malware. However, this isn’t true. Mac’s and Linux machines are affected as well. There are not as many viruses written for Mac and Linux machines, but this is mainly because of their popularity as Operating Systems. Windows OS is the most popular therefore many Malware programmers exists.

    Today a computer without an antivirus is extremely vulnerable. Especially if the computer is connected to Internet or and exchanges files with other computers, which is the case of most of the computers today. More than that, nowadays an antivirus is not enough for avid Internet users. There are so many types of threats that an antivirus alone will not protect you entirely. All computers should have an up to date Antivirus and Antispyware as a minimum. Sometimes, websites that seem inoffensive can infect your computer with spyware, Trojans or even computer viruses.

    Some websites will create deceiving pop-ups to mislead you in believing that your computer is infected. An action is requested on the next step asking you if you want to scan your computer. Many times you don’t have the choice to refuse this action as the pop-up special crafted and you cannot close it. The best thing to do in this situation is to save all of your work and logoff or reboot your computer. Advanced users can alternatively kill the task from the task manager.

    Free Antimalware

    There are a few good choices for people who don’t want to pay for their computer security. There are free antivirus, free antispyware, free personal firewalls, and free anti add-ware. The vast majority of them are only free for personal use. In other words, if your computer is a company computer you should buy a license.
    Don’t forget that you need to have at least an antispyware, an antivirus, and a firewall to be protected, or software that combines all of them.



    A firewall is a must for any laptop, since connecting your laptop in other networks puts a serious threat on the security of your computer. Depending on how your home firewall is configured, if you own one, you might need a firewall on all of your home computers.

    A basic firewall is included with all modern operating systems so you don’t need to buy one. However, if you need a more advanced personal firewall that gives you a very granular control of all your network and Internet activity, in and out, you should consider the free Sygate Personal Firewall, or Online Armor Free, or Comodo firewall which is part of the Comodo Internet Security suite, or Sunbelt Personal Firewall.


    Spyware is one of the most common Malware today. Spyware can range from almost inoffensive pieces of code to software that will damage your computer and make you lose data or steal private information from your computer. A computer without an antispyware protection will be, sooner or later, affected by spyware.
    There are a few free Anti-spyware products on the market. I will first mention the free for anyone “Spybot-S&D!”. It is a good antispyware with a long history on the Market. You need some computer knowledge to configure it for best results. If you need a scan only free Anti-Spyware it’s one of the best choices.
    Ad-aware, the known anti add-ware has evolved to an antispyware program. There is a free limited version.
    Windows Defender is Microsoft’s antispyware solution. Windows Defender is now part of the operating system with Windows Vista and Windows 7. There are Free, (for Personal Use), Security Suites that include antispyware as part of the bundle. See the Security Suites for more antispyware.


    Clamav Logo

    Antivirus has always been a must for any computer that exchanges data with other computers in any way. There are viruses that can even render your computer useless. For instance the virus CIH will corrupt your computer BIOS. The BIOS chip is essential for starting your computer. Other viruses will trash all your hard drive data.

    Free antivirus programs exist on the market. ClamAv is a free, open source, antivirus for both personal and commercial use. Other free for personal use Antivirus include Avira Antivir, Kaspersky Anti-Virus free edition, Norton Security Scan and eTrust EZ Antivirus as a one year trial. There are also free online scanners, many antivirus manufacturers provide an online scanner for free.

    Security Suites

    Security suites are sets of Anti-Malware programs designed to protect against more than one threat. They can contain an Anti-Virus, an Anti-Spyware, Anti-Phishing, a firewall, an Anti-SPAM, as well as other protections against Malware. They are the choice of most of us since they are easy to administrate and don’t require advanced computer knowledge.
    Very popular Free Security Suites are AVG, Avast, Comodo Internet Security, Google Pack – a collection of software that includes an antivirus and an Anti-spyware and Microsoft’s Security Essentials.

    As you see, there are a lot of free choices, so not having an up-to-date Anti-virus and Anti-spyware is free if you can’t afford to pay for one.
    Share you thoughts about Internet Security and your choice of Antivirus.