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Spanning Tree Protocol: Bridge ID, Priority, System ID Extension & Root Bridge Election Process

Posted in Spanning Tree Protocol (STP)

Spanning Tree Protocol: Bridge ID, Priority, System ID Extension & Root Bridge Election Process - 5.0 out of 5 based on 3 votes

In this article we will examine the Spanning Tree Bridge ID structure, explain why it has increments of 4096, how VLAN information is embedded (for Per-VLAN Spanning Tree & multiple STP instances) via the System ID Extension and finally explain how the Spanning Tree Protocol Root Bridge Election occurs.

Understanding Bridge ID, Bridge Priority & System ID Extension

In our earlier article we discussed about the Spanning Tree Protocol, Rapid STP port costs and port states. Before STP decides which path is the best to the Root Bridge, it needs to first decide which switch has to be elected as the Root Bridge, which is where the Bridge ID comes into play. Readers interested can also read our STP Principles, Redundant Network Links & Broadcast Storms article.

Every switch has an identity when they are part of a network. This identity is called the Bridge ID or BID. It is an 8 byte field which is divided into two parts. The first part is a 2-byte Bridge Priority field (which can be configured) while the second part is the 6-byte MAC address of the switch. While the Bridge Priority is configurable, the MAC address is unique amongst all switches and the sum of these two ensures a unique Bridge ID.


The above Bridge ID assumes there is one Spanning Tree instance for the entire network. This is also called Common Spanning-Tree (CST).

As networks begun to grow and become more complex, VLANs were introduced, allowing the creation of multiple logical and physical networks. It was then necessary to run multiple instances of STP in order to accommodate each network - VLAN. These multiple instances are called Multiple Spanning Tree (MST), Per-VLAN Spanning Tree (PVST) and Per-VLAN Spanning Tree Plus (PVST+).

How to Start Windows 8 and 8.1 in Safe Mode – Enabling F8 Safe Mode

Posted in Windows 8 & Windows 8.1

How to Start Windows 8 and 8.1 in Safe Mode – Enabling F8 Safe Mode - 5.0 out of 5 based on 2 votes

This article will show you how to start Windows 8 and Windows 8.1 in Safe Mode and how to enable F8 Safe Mode. Previous Windows O/S users would recall that by pressing and holding the F8 key while Windows is booting (before the Windows logo appears), the system will prompt the user a special menu allowing the user to direct the Operating System to enter the Safe Mode.

When Windows boots, the Safe Mode logo appears on all four corners of the screen:

windows-8-enable-f8-safe-mode-1Figure 1. Windows 8/8.1 in Safe Mode

Occasionally, Windows will not allow you to delete a file or uninstall a program. This may be due to several reasons one of which can be a virus, a malware infection or some driver/application compatibility. Windows may also face hardware driver problems that you are unable to diagnose in the normal process. Traditionally, Windows provides a Safe Mode to handle such situations. When in Safe Mode, only the most basic drivers and programs that allow Windows to start are loaded.

Unlike all other Windows operating systems, Windows 8 and 8.1 do not allow entering Safe Mode via F8 key by default. If you are unable to boot into Windows 8 or 8.1 after several attempts, the operating system automatically loads the Advanced Startup Options that allow you to access Safe Mode.

For users who need to force their system to boot into Safe Mode, there are two methods to enter the Advanced Startup Settings that will allow Windows to boot into Safe Mode.


Method 1 - Accessing Safe Mode in Windows 8 / Windows 8.1

How to Enable & Use Windows 8 Startup Settings Boot Menu (Workstations, Tablet & Touch Devices)

Posted in Windows 8 & Windows 8.1

How to Enable & Use Windows 8 Startup Settings Boot Menu (Workstations, Tablet & Touch Devices) - 5.0 out of 5 based on 1 vote

The Windows 8 Start Settings Boot Menu allows users to change the way Windows 8 starts up. This provides users with the ability to enable Safe Mode with or without Command Prompt, Enable Boot Logging, Enable Debugging and much more. Access to the Setup Settings Boot Menu is provided through the Advanced Startup Options Menu as described in detail below. Alternatively users can use the following command in the Run prompt to restart and boot directly into the Advanced Startup Options Menu:

shutdown /r /o /t 0

While not enabled by default, users can use the F8 key to enter Safe Mode when booting into the operating system, just as all previous Windows versions. To learn more on this, read our How to Start Windows 8 and 8.1 in Safe Mode – Enabling F8 Safe Mode article.

Enabling the Windows 8 Startup Settings Boot Menu via GUI

Start with the Windows 8 Start screen. Type the world advanced directly, which will bring up the items you can search. You may also slide in from the right edge, tap/click on the Search Icon and type advanced into the resulting dialog box. Within the Search items listed, tap/click on Settings:

windows8-startup-settings-boot-menu-1Figure 1. Search Settings

 Windows will now show you the Advanced Startup Options within a dialog box as shown below:

IP Subnet Calculator

Posted in Network Tools

IP Subnet Calculator - 5.0 out of 5 based on 5 votes

This free online Subnet Calculator provides a fast and easy way to calculate all aspects of any IP Address and Subnet Mask. Simply enter your desired IP Address and Subnet Mask below and press Calculate. The results will appear in the fields located to your right side.

    Enter IP Address and Subnet Mask Below
  IP Address: Start Host Address:
  Subnet Mask: End Host Address:
      Max No. of Hosts:
      Network Address:
  Additional Information:

Broadcast Address:
Network Class:
Network Address Size (Bits):
Host Address Size (Bits):

How to Join a Windows 8, 8.1 Client to Windows Domain - Active Directory

Posted in Windows 8 & Windows 8.1

How to Join a Windows 8, 8.1 Client to Windows Domain - Active Directory - 5.0 out of 5 based on 2 votes

In this article, we will show how to add a Windows 8 or Windows 8.1 client to a Windows Domain / Active Directory. The article can be considered an extention to our Windows 2012 Server article covering Active Directory & Domain Controller installation.

Our client workstation, FW-CL1, needs to join the Firewall.local domainFW-CL1 is already installed with Windows 8.1 operating system and configured with an IP address and a DNS server set to, which is the domain controller. It is important that any workstation needing to join a Domain, has its DNS server configured with the Domain Controller's IP address to ensure proper DNS resolution of the Domain:

windows-8-join-active-directory-1Figure 1. FW-CL1 IPconfig


Now, to add the workstation to the domain, open the System Properties of FW-CL1 by right-clicking in the This PC icon and selecting properties:


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