Tag Archives: cases

How to make a Loopback Cable

Why do I need a loopback cable?

Sometimes in order to test a computer’s hardware or software we need a network link for the network adapter. The solution, very often, is to carry around a hub. A loopback software adapter sometimes could help but in many cases it doesn’t work.
The best solution is to create a loopback cable. The loopback cable, or loopback addapter, will work as the computer, or router, or other networked device, was connected to a real network transmitting and receiving packets. The packets are sent and received in a loop, this kind of setup allowing the technician to troubleshoot hardware.

What is a loopback cable?

A loopback cable redirects the output back into itself. This effectively gives the NIC the impression that it is communicating on a network, since its able to transmit and receive communications.

How to make a loopback cable

The short description for a 100T base Ethernet loopback cable:
Redirect Pin 1 to Pin 3 and Pin 2 to Pin 6.
The detailed explanation with pictures follows:
Materials needed:
Good quality Crimper
Cutter pliers
RJ45 plug
Utility knife
UTP cable
Tools needed for crimping
 
Cat 5 Twisted Pairs Take a CAT3 or CAT5 UTP cable and strip the jacket trying to preserve the jacket intact, as you will need it later.
Maintain the wire twists as this will prevent electromagnetic interferences between the two pairs. Untwist the least possible so you could insert the wires into the RJ45 plug. For a 100T base loopback you only need two pairs, I choose orange and green pairs.
Bend the orange pair at the middle making a U shape.
CAT 5 twisted paires

Insert the Orange pair as follows:
White-Orange wire into the pin number 1 and pin number 3 and the solid Orange wire into pin number 2 and pin number 6. Try do insert the four ends at the same time as this is easier.

Pinout RJ45 Plug Loopbac
Click to enlarge
Pinout loopback cable

Crimping the cable

At this point you can crimp your plug for a 100T base loopback cable. Make sure you insert the cable jacket before crimping. The jacket has to be inserted into the plug about an inch so that it’s crimped in and offers rigidity to the loopback cable.

If you want your loopback cable to work at 1Gb you need to insert the second pair, (green), insert the cable jacket and only crimp after that. The green pair is inserted as follows: solid-Green wire in the pin 4 and pin 7 and white-green into 5 and 8.

Improve this article by commenting and asking questions.

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.
    IPCONFIG
    In a web browser type: http://IPADDRESS where IPADDRES is your router.
    For instance if your router’s (gateway) IP address is 192.168.200.1 the address you are looking for is: http://192.168.200.1.
  • 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.

    Domain Name Registration Spam – Scam

    The Domain Name Scam

    The Chinese Domain Name Scam is taking proportions and many of us received scary emails starting with this paragraph:
    We are a domain name registration and dispute organization in Asia, which mainly deal with the global companies' domain name registration and internet Intellectual property right protection in Asia. Currently, we have a pretty important issue needing to confirm with your company.
    On Nov 26, 2010, we received an application formally, one company named “Fake Company Holdings Ltd.” wanted to applied for the Internet brand “yourCompanyName.com” and some domain names through our body.

    Now at first sight this looks very scary and the first reaction is to reply. Don’t do that. Delete the email right away and don’t bother unless protecting the Trademark is an issue for you. Read these two posts about how this scam messages can help you with that:
    Domain Names Scam Explained
    Trademark and Domain Names Protection

    How does the Domain Name Scam work?

    The spammer collects information from the Domain Name registration which is, in most of the cases, public. This information contains the owner name, the email address, and of course the Domain Name. This information is the base of an email sent to the CEO. The email informs the owner that another company is trying to register the domain name in cause but for another TLD.
    As the owner of the domain you “get the benefit of being announced of this purchase” and are being offered to buy it yourself. For instance I own head-massage.net and someone is trying to register head-massage.tw and head-massage.cn, etc… Other country-specific flavors (.asia, .biz, .cc, .cn, .com. cn., .hk, etc.) can be mentioned. You are informed about this and offered to buy the domain or the domains. The email is devised in such way that your domains even if you don’t need it.


    An example of a Domain Name Spam email

    These emails are personalized to the owner/manager of a commercial Internet brand and insinuates that the brand is at risk due to a third party application being made for the respective trademark name. The nice foreign domain registrar they are will ask you if you want to secure all of the variants of your Domain Name so that you can protect your Internet brand.

    Most of these SPAMS have Chinese senders. The email content is changing becoming more and more persuasive and subtle.
    If you received one of these spams, paste a copy of the email in the comments. I also work as a SYS-Admin for a company with an important Domain Names portfolio and we get quite a lot of these.
    Here is a copy of one of these email messages:
    Subject: URGENT---dispute of internet intellectual property safeguard
    (If you are not the person who is in charge of this, please transfer to the right person/department. Thank you.)

    Dear CEO,

    We are the department of registration service in China.we have something need to confirm with you.We formally received an application on April 27, 2009,One Japan company which self-styled "Path soft investment corp" are applying to register (my-head-massage head-massage) as internet brand name and domain names as below (head-massage.cc head-massage.name head-massage.com.hk my-head-massage.name my-head-massage.cc my-head-massage.com.hk my-head-massage.ae my-head-massage.tel my-head-massage.my head-massage.ae head-massage.tel head-massage.my. .etc).

    After our initial checking,we found the internet brand name and these domain names being applied are as same as your company’s, so we need to get the confirmation from your company.If the aforesaid company is your business partner or your subsidiary company, please DO NOT reply us,we will approve the application automatically.If you have no any relationship with this company,please contact us within 10 workdays. If out of the deadline,we will approve the application submitted by "Path soft investment corp" unconditionally.

    Please forward the email to your decision maker,and let them contact me in time,so that we can handle this in reasonable,Look forwarding to hearing from you.

    Best Regards,

    Jake Shen
    Senior Consultant

    If you received a similar letter please drop it in the comments area so we would have more examples.