UEFI – Unified Extensible Firmware Interface

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UEFI

UEFI Overview:

Your PC needs software to make it usable. Specifically, it needs software to control things before the Operating System software can take over. The BIOS or UEFI are options for this software. They allow you to control powerful characteristics of the machine, and they may also contain diagnostic and testing software for the system. A great example of using this software is to set the boot order of the device. Should it try and find the operating system for boot from a USB device first, or should it use the local hard disk drive first?

The Details:

Why did engineers try and improve upon the existing Basic Input/Output System (BIOS) by creating the UEFI? Here are just some of the reasons:

  • They wanted better security; they wanted to ensure they could better protect the pre-boot processes on the PC
  • They wanted to make faster start times possible for a PC
  • They wanted to improve the ability of a PC to resume from hibernation
  • They needed to provide support for hard drives larger than 2.2 Terabytes
  • They wanted to provide support for 64-bit firmware device drivers
  • They wanted to create new software that would be backwards compatible with hardware reliant on a BIOS

The UEFI is controlled by the Unified EFI Forum. This forum is an alliance between many PC giants, like Apple, Dell, Microsoft, etc.

Unlike the BIOS, UEFI does not rely on a boot sector. The UEFI specification uses a boot manager as part of the UEFI specification. When a computer is powered on, the boot manager checks the boot configuration and, based on its settings, loads and executes the specified operating system loader or operating system kernel. The boot configuration is a set of global-scope variables stored in NVRAM. This includes the boot variables that indicate the paths to operating system loaders or kernels.

Operating system loaders can be automatically detected by a UEFI implementation, which enables easy booting from removable devices such as USB flash drives. This automated detection relies on a standardized file path to the operating system loader, with the path depending on the computer architecture. Booting UEFI systems from GPT-partitioned disks is commonly called UEFI-GPT booting. It is also common for a UEFI implementation to include a menu-based user interface to the boot manager, allowing the user to manually select the desired operating system (or system utility) from a list of available boot options.

Want more information? Wikipedia has it here!

Subnetting – Hosts Per Subnet

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subnetting

The Joys of Subnetting Knowledge:

Remember, while practicing just how fast you can ace subnetting questions in the certification environment is always worthwhile and fun, you do want to make sure you understand exactly why you are going through the exercise to begin with. You also want to be sure you understand how subnetting fundamentally works. This is often referred to as subnetting “longhand”.

NOTE: Some of the best and trusted online video vendors have excellent courses that are dedicated just to the topic of subnetting. One of those vendors is ITPro.TV.

ICND1 Sample Question:

You have run the ipconfig command and discovered your IP address and mask are 192.168.20.102 and 255.255.255.224. How many hosts are permitted on your subnet?

Step 1: I reference the Powers of Two chart I created on my scratch paper when I encountered the first question. Adding 128 + 64 + 32 = 224. There are 3 bits used for subnetting and that leaves 5 bits for hosts.

2^7=128  |  2^6=64  |  2^5=32  |  2^4=16  |  2^3=8  |  2^2-=4 | 2  ^1=2  |  2^0=1

Step 2: The equation for the number of hosts per subnet is 2^h – 2 where h is the number of host bits. From the chart I see that 2^5  = 32. 32-2 = 30 hosts per subnet! Too easy!

As always, let us know in the comments if you have a quicker approach.