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Beginner at VLANs needs guidance


I would like to find more information about implementing a VLAN in my current envirnoment. Can someone point me in the right direction?

From what I've read so far, each VLan cannot communication with each other. In order for each VLan to communicate, I would need a router.

What is the difference between subnetting and using a VLAN? Which is better to reduce traffic?

I currently have a flat network structure and would like to increase bandwidth.




Re: Beginner at VLANs needs guidance

Hello Matt,

To answer your question about the difference between subnetting and using a VLAN:

Subnetting is something you do on layer 3, (IP). Typically the subnets match with layer2 segments. That is, normally you allocate an IP range to each cable-segment. A segment consists of a number of ethernet ports that are physically interconnected. The segments can be created by using conventional hubs, or more sophisticated, by assigning VLANs.




Re: Beginner at VLANs needs guidance

Hay Matt,

In regards to what is better to reduce traffic there's no good answer. If you want to break your collision domain within the switch then you need to implement VLANs, but if you still want to have your VLANs to still communicate you need to implement an inter-VLAN routing using a router and hence using subnetting. So in all it's not choosing between the two but using VLAN and subnetting together that makes it more efficient to reduce traffic.

The biggest advantage I see using both is reducing the amout of ethernet port I use on my routers to break up my LAN, because you need to use subinterface for inter-VLAN routing. So that means 1 physical interface to use for 2 or more subnets. Hope that helps.

New Member

Re: Beginner at VLANs needs guidance

By going to a switched network using vlans you can affectively double your bandwidth by utilizing full-duplex mode, standard Ethernet is half-duplex…if you have 100baseTX then full-duplex would give you 200Mbps bandwidth. Also vlans give you more control/security over who belongs to which resources, especially if someone moves offices(diff floor, diff build,diff subnet) they can still be in same vlan and have the same access.

Hope this helps!

New Member

Re: Beginner at VLANs needs guidance

Hi Matt

- Some more information for you. First, I'd like to make correction to the 3rd posting (melimel21) about what he/she said in relation to collision domain. When you move from a hub network to a switch network, each port on a switch is considered to be a separate colision domain. Theoreticalyl there are NO collision when you're using a switch.

- I agree with the 2nd posting that subnetting is a L3 option.

- For discussion, lets assume that you have NOT moved from hub to switch and want to subnet your network. Doing this, you'll end up with more than 1 logical network (directly based on the number of subnets you want you have) AND STILL remain with ONE collision domain.

- Which is a better method to reduce traffic (VLAN or subnet)? Well, the answer would be a combination of both. Subnetting will reduce the amount of broadcast/multicast in your network and ideally each subnet will be associated with one and only one VLAN. What I do with my network is to give each department (in a building) with a /25 (126 possible hosts) and their own VLAN identity. This way, I can control the network a lot better.

Hope this will help you in some way.

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