Best practices VLAN per Switch and Subnet

[LetMePass]

Hi People,

I do some research to get a better understanding about how VLAN and Subnet work but they are very similar. I am looking at a diagram that leaves me puzzled.

 

One of the advantages of having VLAN is to avoid unnecessary work such as deploying extra network hardware and cabling so hard to understand why three switches are required for VLAN 1 and VLAN 2 instead of one.

Personally, I would do that:

Now, perhaps I have missed something. Perhaps devices are not located in the same location and for some reason more switches had to be added.

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Apparently you also need VLAN AND subnet, no subnet no VLAN. But you can have subnets without VLAN.

Subnet: reduce unnecessary traffic, make network easier to manage and less congested, improve security. One router to per subnet, require HW.

VLAN: reduce the amount of HW, In a VLAN, the computers, servers, and other network devices are logically connected regardless of their physical location.

Also improve security, traffic management, make network simpler.

Feel free to correct any of my assumptions.

Best Regards,

Chris

[M02@rt37]

Hello @LetMePass 

VLANs and subnets serve distinct purposes in network design. VLANs provide logical segmentation within a physical network, allowing devices to communicate as if on the same network despite physical separation. The choice of multiple switches for a VLAN depends on factors like redundancy and scalability. Subnets, on the other hand, divide an IP network into smaller, manageable segments, reducing unnecessary broadcast traffic and enhancing security. While often used together, subnets and VLANs are not strictly interdependent, and their implementation can vary based on specific network requirements, physical layout, and design considerations.

[LetMePass]

Hi M02@rt37 

You get a good point; redundancy. That's what I overlooked!

Another factor worth mentioning is that subnet and VLAN have a common goal of reducing the broadcast domain size.

They have different types of broadcasts, as @tmusabaika2017 correctly pointed out in a different thread.

https://learningnetwork.cisco.com/s/question/0D53i00000Kt5cvCAB/layer-2-broadcast-layer-3-broadcast

"A basic major difference is that a Layer 3 broadcast uses the ip address 255.255.255.255 while a Layer 2 broadcast uses the physical / MAC address FF:FF:FF:FF:FF:FF"

[M02@rt37]

@LetMePass 

Redundancy is a critical consideration in network design to ensure high availability and fault tolerance. Multiple switches for a VLAN, connected through trunk links, provide redundancy by allowing traffic to flow through alternative paths in case of a link or switch failure. This enhances network reliability.

Furthermore, subnets and vlan both contribute to the reduction of broadcast domains, addressing different aspects of the network. Subnets operate at the network laye and help reduce broadcast traffic by segmenting IP networks. Routers are used to interconnect different subnets and control the flow of broadcast traffic between them. VLAN operate at the data link layer and provide logical segmentation within a switch. Devices within the same VLAN are in the same broadcast domain, and devices in different VLANs are in separate broadcast domains.