I personally feel that the concept of VLANs, simple as it is, is extremely
misunderstood by most people in the industry and for that reason, I strive
to present it accurately. Consider these common questions:
Do I need a router between my VLANs?
Do I need an IP address on my VLANs?
Can I route between VLAN 1 and VLAN 2 with just a switch?
Can I have multiple subnets on the same VLAN?
I've heard these types of questions many times and all of them would be
reduced if people stopped thinking about VLANs in a layer three context. If
one could prevail upon students the concepts of collision and broadcast
domains and the role routers play in bounding and interconnecting them, the
concept of VLANs would be a very logical next step. Telling people that
VLANs are subnets simply confuses the matter and in reality is anything but
the truth. Certainly a one to one mapping of VLANs to IP subnets would be
ideal, but is not always the case nor is a requirement.
In IP training, I do see the value of having people think about VLANs
containing single IP subnets, but I still feel you must make sure people
understand the exclusivity of the two concepts. IP is still pretty low on
the chart of most popular protocols in use on end stations last I checked :)
Pete
*********** REPLY SEPARATOR ***********
On 7/24/2001 at 5:47 PM Priscilla Oppenheimer wrote:
>At 01:03 PM 7/24/01, Peter Van Oene wrote:
>>I beg to differ slightly on the concept of VLANS. A VLAN, as I'm sure you
>>know, is a broadcast domain and makes no assumption of nor has any
>>dependance upon layer three protocols.
>
>I agree in theory. But in practice a VLAN is an IP subnet (on IP networks)
>and it helps to think of it this way when designing and troubleshooting. I
>get this from Dan Farkas, CCIE and CCSI, author of switching papers at
>Certificaton Zone. http://www.certificationzone.com. (No, this is not
>another ad for that great service. ;-) But Dan says that he encourages his
>students to use the terms broadcast domain, subnet, and VLAN
>interchangeably. It helps them understand traffic flow, etc. I think it
>might help the poster....
>
>Priscilla
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=13685&t=13465
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