Ok, one more round of nit picky comments and I'll quit :)
> >
>> > Do I need a router between my VLANs?
>
>If you want the VLANs to communicate with each other. Are these trick
>questions? ;-) I realize there are cases where you don't want them to
>communicate. I guess that is what you are getting at.
>
If you want VLANs to share the same broadcast domain, you bridge them.
Telling people they need a router between them makes people think that
VLANs have some magical layer three capabilities which leads to the
above question. Do people ever ask if you need a router between your
layer 2 broadcast domains? No. Because it used to be obvious. If you
want to route, you need a router. VLANs and the similarly misunderstood
Layer 3 switch haven't changed that caveat.
>> > Do I need an IP address on my VLANs?
>
>Some sort of network-layer addressing is required for end stations to
>communicate using typical applications. There are some cases where
>network-layer addressing is not used, of course, but that sort of
>communication is being phased out.
Again, if you want to route layer three protocols, you use a router. In
multiprotocol networks, such as those tested on the CCIE exam, it is
often necessary to support a mix of protocols, some of which need to be
routed across broadcast domains while others are bridged. Understanding
this is much easier when you don't believe in the tooth fairy.
>
>> > Can I route between VLAN 1 and VLAN 2 with just a switch?
>
>No, not a Layer 2 switch.
Bad question :) You can certainly bridge two VLANs, essentially
creating one. I should have said connect vs route. The point is to
illustrate the difference between layer two broadcast domains and
routing, thus reinforcing the point that if you want to route, you use a
router. There are no exceptions to this rule.
>> > Can I have multiple subnets on the same VLAN?
>Yes, but they won't communicate without a router. A station trying to
>communicate with a station in a different subnet ARPs for its default
>gateway. Sure there are exceptions with strangely behaving IP stacks
and
>errors with subnet mask configurations, etc., but let's consider the
>typical case.
This is my point. To route, you need a router. VLANs haven't changed
this whatsoever.
I simply find that too many people misunderstand the VLAN concept
simply because vendor marketing has confused the issue and numerous
pieces of literature make the layer 3 to VLAN binding without properly
developing the difference.
Nit picky I know, but its a pet peeve.
Pete
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=13858&t=13465
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