Vicky's Technical Blog

I have been hearing a lot on SDN for quite a long time. There are many articles on the web which talks about it but does not adequately explain what IS SDN really. I finally decided to write on SDN from my perspective. Let’s start with a simple example. We have CISCO Router (I like cisco). I want to check whether my CISCO Router can ping an IP on the Internet. To do this I will carry the following steps: 1. telnet or ssh into the router 2. ping an IP address on the internet (8.8.8.8) If I have to do this regularly it becomes a boring thing. What if I can write an Application which can telnet/ssh into my router, then perform a ping and check whether the ping was successful or not? This is where SDN comes into play. SDN allows you to programmatically configure or run commands on your switches and routers. I think that the right word for this should have been Programmable Networks (I have seen this on some networking vendor’s website) To make SDN ha...

Windows 8 Codec Pack is a FREE software which allows you to play lots of file formats such as flv and mkv in your Windows Media Player . The name of the software is misleading I think…it supports not only windows 8/8.1 but also 7, Vista, XP, 2000, 2008, & 2003. The software is compatible with Microsoft Windows Media Player 9, 10, 11, & 12. Now you can relax and play all your files in Windows Media Player . You don’t need any separate player for playing video files such as flv and mkv . From the Windows 8 Codec Pack website : Compression types that you will be able to play include: x265 | h.265 | HEVC | 10bit x264 | x264| h.264 | AVCHD | AVC | DivX | XviD | MP4 | MPEG4 | MPEG2 and many more. File types you will be able to play include: .bdmv | .evo | .hevc | .mkv | .avi | .flv | .webm | .mp4 | .ts | .m4v | .m4a | .ogm | .ac3 | .dts | .flac | .ape | .aac | .ogg | .ofr | .mpc | .3gp and many more. Codec's Explained : A codec is a piece of softw...

The world backup day is an initiative to make people aware on the importance of backup. The official website of World Backup Day is at http://www.worldbackupday.com/en/ Your hard disk, smartphone or laptop may not be always loyal to you. Computers get infected with viruses, smartphones are lost and your hard disk gets fried. “Remember backup is a continuous process not a one off process. You must always backup your data not only on 31 March.” WHAT IS BACKUP? Let’s quote exactly from the website: A backup is a second copy of all your important files — for example, your family photos, home videos, documents and emails. Instead of storing it all in one place (like your computer), you keep another copy of everything somewhere safe. WHY SHOULD YOU BACKUP ? Your data is valuable. It’s important because you might need it for personal and professional reasons. Your ebooks, your final year dissertation, your source codes, your customer list, your chi...

The following has been taken from  VMware Knowledge Base  -  KB 1025279 Snapshots are not backups . A snapshot file is only a change log of the original virtual disk. Therefore, do not rely on it as a direct backup process. The virtual machine is running on the most current snapshot, not the original vmdk disk files. Snapshots are not complete copies of the original vmdk disk files. Taking a snapshot does not create a complete copy of the original vmdk disk file, rather it only copies the delta disks. The change log in the snapshot file combines with the original disk files to make up the current state of the virtual machine. If the base disks are deleted, the snapshot files are useless. Delta files can grow to the same size as the original base disk file , which is why the provisioned storage size of a virtual machine increases by an amount up to the original size of the virtual mach...

About 5 minutes ago I found a nice freeware tool ( InstalledDriversList ) which can be used to view the installed drivers on your PC. From the official website of InstalledDriversList : InstalledDriversList is a simple tool for Windows that lists all device drivers that are currently installed on your system. For every device driver, the following information is displayed: Driver Name, Display Name, Description, Startup Type, Driver type, Driver Group, Filename, File Size, Modified/Created Time of the driver file, and version information of the driver file.  If the driver is currently running on Windows kernel, the following information is also displayed: Base Memory Address, End Address, Memory Size, and Load Count. This tool may be used to identify which drivers are causing trouble on Windows. Again quoting the original text: Green Icon - The driver is running on Windows kernel. Yellow Icon - The driver is not running on Windows kernel. Red Icon - The driv...

I found the following “laws” from Murphy's computers laws .  I selected the best ones which I think are true, funny and interesting. Read them and have a nice day. If a program is useless, it will have to be documented   Bugs will appear in one part of a working program when another 'unrelated' part is modified. Adding manpower to a late software project makes it later. A working program is one that has only unobserved bugs. No matter how many resources you have, it is never enough. Any cool program always requires more memory than you have. When you finally buy enough memory, you will not have enough disk space. Disks are always full. It is futile to try to get more disk space. Data expands to fill any void. If a program actually fits in memory and has enough disk space, it is guaranteed to crash. If such a program has not crashed yet, it is waiting for a critical moment before it crashes.   No matter how good of a deal you get on computer compon...

One good thing to do when working with the command prompt on windows (also known as CMD) is to change its window title. I got this little trick which does the job from a blog on the Microsoft MSDN website. If you have 10 or more windows like this, then  it becomes difficult to manage and work efficiently. After you have opened a new Command Prompt Window, type  title  < text you want to appear in the window title >

Today, after downloading an important attachment from my Gmail Account, I got the following error while trying to open it: Word experienced an error trying to open the file. Try these suggestions: *Check the file permissions for the document or drive. *Make sure there is sufficient free memory and disk space *Open the file with the Text Recovery converter. The solution is to right click the file then on the properties box click unblock.

JEREMY L. GADDIS , owner of  the blog at http://evilrouters.net , has written an excellent tutorial on how to advertise a default route over BGP . The most important part of the tutorial to actually advertise the default route is the following: R3(config)# router bgp 33 R3(config-router)# neighbor 172.16.34.4 default-originate R3(config-router)# neighbor 172.16.35.5 default-originate SOURCES evilrouters.net :  Advertising a default route over BGP

Ever wondered how strong is the SSL encryption we use everyday in our web browser and email clients (e.g Outlook, ThunderBird)? Q: How secure is the encryption used by SSL? A:  It would take significantly longer than the age of the universe to crack a 128-bit key. Understanding SSL SSL uses public-key encryption to exchange a session key between the client and server; this session key is used to encrypt the http transaction (both request and response). Each transaction uses a different session key so that even if someone did manage to decrypt a transaction, that would not mean that they would have found the server's secret key; if they wanted to decrypt another transaction, they'd need to spend as much time and effort on the second transaction as they did on the first.  Of course, they would have first have to have figured out some method of intercepting the transaction data in the first place, which is in itself extremely difficult.  It would be s...

When you are using GNS3 on Win 7/8 and if you stop the router, you get a blue screen saying your PC ran into some problem with the following error: IRQL_NOT_LESS_OR_EQUAL Your PC will restart after this error :( After doing some research on the GNS3 forum and reading the users experience, I found 2 solutions to this problem: 1. Run GNS3 on a LINUX Distro e.g DEBIAN or UBUNTU (FYI: A Linux Distro is always more stable than Windows) 2.If you are not comfortable with LINUX then you can still use WINDOWS but make sure you run the following CISCO IOS Images according to a post (please see extract below) on the CISCO LEARNING NETWORK   by Navneet.Gaur : “These are the stable working IOS images for GNS 3. I have some of them as I own the routers. 1 Cisco 2691 Router | 2600 Series - Extremely stable      c2691-adventerprisek9_ivs-mz.124-9.T7.bin 2 Cisco 3640 Router | 3600 Series      c3640-ik9o3s-mz.124-25...

One of my friend was having a difficult time understanding these 2 terms and was interchangeably using the words speed and bandwidth to mean the same thing where in fact speed and bandwidth are 2 different things. So I decided to write this post and make things clear :) Bandwidth IS NOT Speed Speed is generally used by consumers to refer to how fast they can download files and upload files.  Bandwidth Broadband Internet packages are sold based on their bandwidth, or the size of the "Internet pipe" that is allocated to each user. This number refers to the capacity of the "last mile" connection that connects your home to the nearest aggregation point. In other words, it is the maximum throughput that the user can get on his broadband service. Does higher bandwidth give you faster speed? The analogy of driving on the motorway will help you to understand bandwidth and speed. Imagine that you're driving on a road with 4 lanes in a car t...

On a Saturday night, after happily and proudly connecting my Verbatim USB 3.0 External Drive I was shocked to hear a clicking and fearful noise. I thought the drive has failed. The drive is 1 TB (2.5 inch hard disk). I had to copy some important files from the External drive to my Laptop. I switched to another USB port and guess what... my drive worked correctly J The real culprit was one of the USB ports on my laptop. (Oh My DOG, this USB port is a real B*TCH !!) “Clicking Noise does not absolutely mean that the external drive has failed.” The USB port on my laptop is not faulty – a USB mouse connected on this port works correctly. I did some research to investigate this issue. Other users got similar problem “Low voltage to a hard-drive can mimic all manner of failures.” So, insufficient power from a USB port on a laptop or pc can cause clicking noises on an usb external drive. My drive is safe. I can copy my data from it. Long live my drive J