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RE: VLANs and IPs [1:18164] posted 11/26/2006
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Curt Shaffer wrote:
> I have a question that I just can't get my head around and no
> documentation seems to be clear. Do VLANs need to be different
> IP subnets? 

VLANs  are are just like LANs but instead of being separated physically like
in LANs, VLANs are separated logically.
Just like different LANs need different IP subnets, VLANs need to be in
different IP subnets.

For example if I have 1 network and have everyone
> on a network can I have multiple VLANs in this
> network?

Well you can have multiple VLANSs in the  network if you further subnet the
network . Hope you are okay with subnetting.
Here is an example. If you do subnetting using two bits on the you have the following 2 subnets.
With the above subnets you can then use them for two different VLANs.

 IF not how do dynamic VLANs work? If I have different
> subnets but I have a user that is in a Dynamic VLAN but
> connects to another IP subnet how would they connect back to
> the IP subnet with the original IPs if they have a different
> subnet without needing to do inter VLAN routing 

In order for two hosts in different VLANS to communicate you always need a
layer three device to route between the hosts. You either use a router, or a
multilayer switch.

>...which would
> defeat the purpose of VLANs no? Any insight would be appreciated.

Main purpose of VLANS is to place hosts in different broadcasts domains.
Using a router or a multilayer switch to have different hosts communicate
does not defeat the purpose of VLANS.

> Thanks
> Curt

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