Category Archives: Networking

Encoding vs Encription vs Hashing: Explained in One Word

This could be often confusing so to remember I tried to use one word and a short explanation without getting into any technical details here.


1. Encoding = Translate

It’s goal is to converts data so it can be understood by another system. Security is not it’s concern.
ex. ASCII, Unicode


2. Encryption = Transform

It’s goal is to change the data into a different format so it’s Super Secure and will require a key to unlock. Security is it’s main concern.
ex. DES, 3DES, AES


3. Hashing = un-Touched

It’s goal is to check the data and make sure there was no modification of any kind during the transfer and the data is intact. Integrity is it’s main concern.
ex. MD5, SHA


Just remember the Triple T, Translate, Transform, un-Touched.

I tried to find a word that I can replace un-Touched which starts with T but wasn’t able to find. If anyone can come up with something better please leave a comment and I will replace it.

How to Password Reset on 3850 Switch

Do the regular routine of unplugging the power-cord and holding the mode button and then plugging back until you land in recover mode (switch:)

Now enter the following commands

switch: boot

After reboot

Switch(config)#no system ignore startupconfig switch all
Switch(config)#system disable password recovery switch all
Switch#copy running startup


Authentication vs Authorization

I use to always find these two words confusing. Never use to understand the difference between both and actually both sounded like same with similar meaning. Actually they are not.

Authentication (AuthC) is the process of identifying the authenticity of a user. Is he really the same person he claims to be or he is hiding behind a mask of someone else.

Example: If you have ever been to a convention center (Ex. RSA, Cisco Live etc.) you will first go to the front desk were they will ask you for your name and company ID and also will request you to accompany with a Driver’s License. Now they are trying to Authenticate whether the company badge and the Driver’s License belongs to the same person.

AuthoriZation (AuthZ) is the process of assigning permission or restrictions, in other words what level of access to secure assets or location.

Example: Once your ID is checked at the front desk of the convention center and you are authenticated, a badge (tag) is given to you which might say Guest, Exhibitor or Owner etc. Based on what Authorization or access level you are granted, you can access certain levels and rooms in the convention center.

I hope this clarifies.

Setting up TFTP server on Windows Machine

Go to tftpd32 website.

Click Download from the top menu. Then Select tftpd32 standard edition (installer) and download the exe file.

Start the installer and if prompted with the following screen hit yes.


Select I Agree



Leave the default settings and hit Next.




Leave the default location unless you really have to change it and then hit Install.


Installation should be now complete, simply click close.




From your desktop double-click the Tftpd32 icon.

Once the application starts, select Settings > GLOBAL (Tab) and just check TFTP Server/Client unless you want the others.

Now select TFTP (Tab) > Browse (Base Directory)

I recommend you to create a tftp folder under (C:) drive and select it as below and hit ok:

If it prompts to restart the server please do so. Your ftp server is ready to use.

How to update IOS (XE) on 3850

Step 1: Download and copy the latest IOS (XE) to the 3850 flash via USB or TFTP.

Step 2: Check the mode (Install or Bundle) of the switch by entering following command:

Switch#show version | begin Switch Ports

The out put will be as below:

Note: If the Switch is not in INSTALL Mode it’s highly recommended to switch INSTALL mode from BUNDLE mode. Click here to find out how or enter the below commands:

# software expand running to flash:
(config)#boot system flash:packages.conf

Step 3: Enter the following command to start installing the new IOS using the new code on the flash

Switch#:software install file flash:<New_IOS_File_Name>.bin
Switch#:software install file flash:cat3k_caa-universalk9.SPA.03.03.00.SE.150-1.EZ.bin
Then following will be shown:

Step 4: enter yes and hit enter.


NOTE: Ran into some issue booting 3850. This might be helpful if your Catalyst 3850 Fails to Boot.

3850-access#show boot
Switch 1
Current Boot Variables:
BOOT variable = flash:packages.conf;

Boot Variables on next reload:
BOOT variable = flash:packages.conf
Allow Dev Key = yes
Manual Boot = yes
Enable Break = no

Notice it’s set to Manual Boot = yes

you need to change that to NO

#conf t

(config)#no boot manual


If this also doesn’t fix the boot issue refer the following blog post here.

How to Password Reset on ASA 5505

Step1: Reboot ASA

Step 2: Wait till the you can see following “Use BREAK or ESC to interrupt boot.”  and then hit the ESC key, works on MAC/Terminal as well. (see below)


Step 3: Then you should land in “rommon #0>”

Step 4: Change the confreg valu to 0x41 as it tells to ignore its saved (startup) configuration upon boot

rommon #2> confreg 0×41

Step 5: reboot

rommon #2> reboot

Step 6: After the reboot you need to change the confreg value back to 0x01 and reboot.

ciscoasa(config)# config-register 0x01
ciscoasa# reboot