What's a VLAN?

[Fraoch]

I have been researching VLANs but I don't quite seem to get it.

What is a VLAN? Why would I want or need one for my home network?

Thank you.

 

[thetoad30]

A VLAN is a segregated network but using the same hardware.

It is like how a virtual machine works - you have multiple computers on one set of equipment.

So for example, my VLANs separate all of my heavy-traffic loads to help prevent broadcast storms.

I have my wireless separated from my server traffic, because I know wireless has a lot more "talking" than my servers would. Also, I want my servers to have their own link to my router.

So I have one VLAN that is wireless connected to my switches and router, and one for my servers connected to my switch (the same one) and my router (the same one).

In essence I now have two different networks running over the same hardware. It means I can not have as many switches and routers to run the same equipment.

Normally you'd need one switch and router per network - and then would have to figure out a way to split your internet connection. With VLANs, you can hook everything up and tell the devices (switches and routers) what VLANs you want traffic on and they will take care of the rest.

Does that make sense?

 

[Fraoch]

That makes a lot of sense, thank you thetoad30!

I believe all equipment must be VLAN-capable, correct? All switches should be VLAN-capable "smart" switches and any routers also need to be capable of VLANs?

In essence, can you have two subnets out of the same router on the same patch cables then? Say a 192.168.1.0/24 subnet for your wired traffic and a 192.168.2.0/24 for your wireless traffic coming out of a (hypothetical) single-port router on a single patch cable, then going into a smart switch which will then separate out 192.168.1.0/24 on one port and 192.168.2.0/24 on another?

Is that how it works?

 

[John Kotches]

That makes a lot of sense, thank you thetoad30!

I believe all equipment must be VLAN-capable, correct? All switches should be VLAN-capable "smart" switches and any routers also need to be capable of VLANs?

Yes.

In essence, can you have two subnets out of the same router on the same patch cables then? Say a 192.168.1.0/24 subnet for your wired traffic and a 192.168.2.0/24 for your wireless traffic coming out of a (hypothetical) single-port router on a single patch cable, then going into a smart switch which will then separate out 192.168.1.0/24 on one port and 192.168.2.0/24 on another?

Is that how it works?

No. In the 7 layer model, IP is layer 3 and Ethernet is layer 2. VLAN tagging is in layer 2. A working example has wireless on vlan 200, use wired for vlan 100. The router would be on both VLANs.

All of these are on 192.168.1.0/24.

Your wireless devices would operate only on packets tagged for VLAN 200, wired devices only VLAN 100 tagged packets and the router would see both. You've now isolated the wireless from the wired on the same IP subnet. This is what it's supposed to do.





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[coxhaus]

Vlans divide network switches logically. This helps to contol your broadcast domains and divide slower traffic away from your faster core. The down side is you must route traffic between vlans to be able to pass data between vlans. If you only have one layer 3 device, your internet router, then you are stealing cpu cyles from your download router when you pass data between vlans. It all becomes a balance setting up your network for optimal performance.

 

[Fraoch]

Understood, thanks for the explanations!