DEV Community: Elwin Berrar

Spanning Tree Protocol

Elwin Berrar — Fri, 12 Dec 2025 17:05:34 +0000

To understand how Spanning Tree Protocol (STP) selects the Root Bridge, you first need to understand the concept of the Bridge ID, often called the BID.

The Bridge ID uniquely identifies a switch in an STP topology. It is built from two elements. The first is the extended priority, which is a configurable numeric value.

By default, the priority is set to 32,768. This value is combined with the VLAN ID. For example, on VLAN 1, the calculation becomes 32,768 plus 1, resulting in 32,769.

The second element is the MAC address. This part is used only when multiple switches share the same priority, acting as a tiebreaker.

When these two elements are combined, they form the complete Bridge ID. A typical example looks like this: 32,769 followed by the MAC address AABB.CCDD.EE01.

Root Bridge Election Process

During the Root Bridge election, switches exchange BPDUs, which are Bridge Protocol Data Units. These messages allow each switch to advertise its Bridge ID and learn the Bridge IDs of other devices in the topology.

STP always elects the switch with the lowest Bridge ID as the Root Bridge. The comparison starts with the priority value. If priorities are equal, STP then compares MAC addresses. In that case, the switch with the lowest MAC address is elected.

For example, if three switches use the default priority on VLAN 1, their Bridge IDs might all start with 32,769 but end with different MAC addresses. If SW1 ends in EE01, SW2 in EE02, and SW3 in EE03, SW1 becomes the Root Bridge because its MAC address is the lowest.

The election logic is straightforward. A lower priority increases the chances of becoming the Root Bridge. When priorities are equal, the lowest MAC address wins. In all cases, the Root Bridge is always the device with the lowest Bridge ID in the network.

For more information and a complete explanation of how Spanning Tree Protocol works, including port roles, states, and loop prevention, see this detailed CCNA guide: https://pingmynetwork.com/network/ccna-200-301/how-spanning-tree-protocol-works

The Future of EdTech and IT Certification

Elwin Berrar — Sun, 09 Nov 2025 16:16:03 +0000

The world of education is changing faster than ever, and the IT industry is at the center of it. Traditional schools still play an important role, but they can’t keep up with the speed of technological progress. And honestly, it’s not their fault. Their mission is to provide foundations, not to track every new tool, update, or framework that appears each year.

In reality, technical validation today comes from certification. IT certifications—CCNA, CCNP, AWS, Azure, Linux, and many others—are becoming the true measure of skill. They are practical, focused, and constantly updated. They give learners a direct way to show what they can actually do, not just what they have studied years ago.

People need better ways to learn. They need environments where they can grow, measure their progress, and build confidence. Not everyone thrives with static courses or traditional academic paths. Learning today needs to be flexible, interactive, and rewarding.

With PingMyNetwork, our goal is to support this evolution. We want to build tools that help both beginners and professionals improve their technical abilities—not just passively consume content. One day, we hope to bring our platform into classrooms and schools to support teachers with modern, adaptive training that prepares students for real-world challenges.

We believe in a future where learning feels alive.
Where you can see your progress.
Where effort leads to rewards.
Where motivation grows as your skills grow.

The IT field will keep evolving. The way we learn must evolve too. And if we build the right tools, everyone—from students to seasoned engineers—will feel empowered to move forward and stay confident in their roles.

This is the future we want to help create.

Understanding 802.1Q Trunking – A Core Concept in Networking

Elwin Berrar — Thu, 23 Oct 2025 09:55:59 +0000

Hey everyone 👋

This is my first post here, and I’m really happy to join the DEV community — great to see so many people sharing knowledge here.

I’ve been working on networking projects lately and wanted to share one of the most essential CCNA concepts: 802.1Q Trunking.

When you configure VLANs, you quickly notice that each VLAN is isolated to a single switch.

But what happens when you want VLANs to communicate across multiple switches?

That’s exactly where 802.1Q comes in.

What is 802.1Q Trunking

802.1Q Trunking is an IEEE standard that allows multiple VLANs to travel over a single physical link.

Each Ethernet frame is tagged with a VLAN ID, letting the receiving switch know which VLAN the frame belongs to.

This makes it possible for VLANs to extend beyond a single switch, connecting entire networks logically.

Example topology

Below is a simple diagram showing two switches connected by a trunk link.

Notice how VLAN 10 and VLAN 20 can communicate between SW1 and SW2 using 802.1Q tagging.

Key takeaways

Access ports handle traffic for one VLAN only.
Trunk ports carry traffic for several VLANs using 802.1Q tags.
The native VLAN stays untagged by default.

It’s a fundamental mechanism for VLAN communication across a network.

If you’d like to go deeper with diagrams and configuration examples, I wrote a detailed explanation for learners, it’s totally free to read:

👉 802.1Q Trunking Explained (Free Guide)

Thanks for reading.

I’m new here, so feel free to share your feedback or tips for improving future posts.