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Thread: VLAN vs Subnet

  1. #1
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    Default VLAN vs Subnet

    Is a VLAN a subnet? true or Flase...
    saw this posted on the cisco network academy facebook page and thought it was an awesome question.

    i think they are same, reason being that they both need different networks for them to function and for inter vlan or inter subnet communication to take place they need a layer device.

    what say you?
    Last edited by frass2000; Sep 4, 2011 at 11:44 PM.

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    I would say false. Isnt a VLAN what allows you to to create a Subnet? Im thinking what if I created Vlan1&Vlan2 and have the same address scheme and default mask wouldnt they be considered to be in the same subnet? granted you need a router for inter-vlan communication but its still the same subnet.
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    Quote Originally Posted by duster View Post
    Isnt a VLAN what allows you to to create a Subnet?
    No, VLANs aren't needed to create subnets. I agree without your other point...
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    VLANS are not subnets.. nodes can have different subnets and be within the same location. subnets are particularly a logical separation determining the IP Address. VLAN's on the other hand are supposed to be devices that are physically separated but are on the same network through layer 3 devices.. thus it being a VIRTUAL LAN
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    Vlans=broadcast domains=subnets
    Yea u can have vlans with the same layer address scheme but then they wudnt be able to communicate via a layer device hence each vlan wud have to be on a different subnet for them to function properly
    Last edited by frass2000; Sep 4, 2011 at 11:45 PM.

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    lol frass you are absolutely correct.....a virtual lan is method of segmenting network..by creating subnets (vlans)....firstly vlans operate technically in the same way as a subnet.....broadcasts are limited to other devices on same subnet (vlan)...all devices on same subnet can communicate with each other...and to get off one network...for example 192.168.1.0 to another ie. 72.27.16.0 ..(Routing)...then you need a gateway....(a layer 3 device that will route packet from one network to another)....if i am a student on one subnet....and there is no gateway device....can i communicate with the person on a HR dept subnet...answer no....why i am on a different network....breaking up your network into smaller ones is one way of reducing the sheer amount of broadcast on any ONE network....a vlan does just that...so does a subnet....a broadcast is limited to devices on the same Network......thus a broadcast domain is limited to jus the network the broadcast is on....hence vlan=subnet.....vlan=broadcast domain...same thing....frass it wowed me the first time i found out.....weird huh...anyhow frass is correct guys...

    @vylle....lol..dude let me understand this....i am on a network right.....there is a router attached to a switch....k....the router ..well it has four interfaces.....fast ethernet ....ok
    connected to four ports on a 24 port switch...with me?....i configure the router interfaces to 192.168.1.0 - 192.168.4.0 for the four interfaces..with me....at this point..if i plug 4 pcs into the switch n put each in a different "subnet".....could i communicate with the pc next to me...yes you could...and you are both on different subnets...dont it....well guess what....all vlan is doing is the same thing....whats the big difference then its a switching technology....switches know only mac address....vlans were created to help the switch make better traffic management deccision...vlans go hand in hand with spanning tree, vtp, etc. so here is the deal....each vlan on the switch is like a network....and n it keeps an account of which "ports" on the switch are on each network....so thats why u would not be able to jus replace a ip address on a pc attached to a port specifically assigned to a vlan.....get it...but broadcasts traffic is not going to all the ports on the switch n the network...by default the switch forwards broadcasts....only the ports that are in say....ie vlan Techjamaica...receives broadcasts from other pcs on that vlan.....sounds familiar to subnets....that because the application of both technology is virtually..pun intended the same....i cant leave a subnet or vlan without a layer 3 device....cant broadcast outside of vlan or subnet by default.....can communicate freely with devices on my own vlan or subnet....vylle its the same thing boss trust di i....dem jus pretty it up...same principle..different application...dont look at the concepts....look at what the resultants are...what do they do...hope it helps

    all it is that one is a Layer 3 technology (ip addressing - subnets).....versus Layer 2 (vlan).....same thing dem do
    Last edited by ramesh; Sep 5, 2010 at 10:50 PM. Reason: merged posts
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  7. #7
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    yes it is.......... when you create a vlan an additional broadcast domain is created and remember in order for hosts in different t ocommunicate you need a layer 3 device and this is where a router comes in.........

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