Mastering Inter-VLAN Routing: A Comprehensive Guide with Interview Questions

In the ever-evolving world of computer networking, Virtual Local Area Networks (VLANs) have become an essential tool for organizing and managing network traffic. However, as networks grow more complex, the need for communication between different VLANs arises, leading to the concept of inter-VLAN routing. Whether you’re a network administrator, a cybersecurity professional, or an aspiring network engineer, understanding inter-VLAN routing is crucial for maintaining efficient and secure network operations.

This comprehensive guide will not only explain inter-VLAN routing in simple terms but also provide you with a collection of interview questions and answers to help you prepare for your next networking interview.

What is a VLAN?

Before diving into inter-VLAN routing, it’s essential to understand the concept of VLANs. A VLAN is a logical grouping of network devices and resources that behave as if they are part of the same physical network, even though they may be physically located on different network segments. VLANs help to reduce broadcast traffic and enhance network security by isolating traffic within each logical group.

Why Inter-VLAN Routing is Necessary

While VLANs are excellent for segmenting networks and controlling broadcast domains, they also create a challenge when devices from different VLANs need to communicate. Inter-VLAN routing is the process of forwarding traffic between different VLANs, allowing devices in one VLAN to communicate with devices in another VLAN.

Without inter-VLAN routing, devices in separate VLAN

Scenario Based Interview Question of VLAN For Network Engineer.


What is the inter-VLAN routing?

Inter-VLAN routing is the ability to route, or send, traffic between VLANs that are normally blocked by default. Switches and VLANs work at the MAC address Layer (Layer 2). Traffic can’t be routed between VLANs at Layer 2 based on MAC addresses.

What are the steps which must be completed in order to enable inter-VLAN routing?

What are the steps that must be completed in order to enable inter-VLAN routing using router-on-a-stick? Configure the physical interfaces on the router and enable a routing protocol. Create the VLANs on the router and define the port membership assignments on the switch.

What is a disadvantage of using router on a stick inter-VLAN routing?

If the router fails, there is no backup and that may become the bottleneck in the network, effectively making all inter-VLAN communication impossible. Moreover, since all VLANs must traverse one router, there is a great potential in insufficient bandwidth provided for all network connections.

How many interfaces are needed in a router on a stick implementation for inter-VLAN routing among four VLANs?

Router-on-a-stick inter-VLAN routing can utilize a single router interface as a trunk link to receive and forward VLAN traffic and does not require multiple interfaces.

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