I appreciate everyone's input on this subject to help me understand this
concept.
As far as the newbies comment goes - I most definitely am. I'm about as
green as they come. I have both my CCNA and my CCDA, but my only real
experience is installing 2 T1s (at different locations) and configuring NAT
for them. I have large amount of knowledge, just no experience. It has been
my goal and my dream to become a serious network engineer for the last 6
years, but I just cannot seem to get a job that offers any experience.
Everytime I get a "network" position, I just seemed to end up doing desktop
support.
When I first heard the term Layer 3 switching (some 4 years ago now) the
first thing that popped into my mind was a switch that can route. I never
even heard of a VLAN until a couple of years ago.
The Cisco Study guide starts off talking about VLANs, and moves right into
Inter-VLAN routing without ever really discussing Layer 3 switching as a
seperate process. This is really where my confusion started. The book makes
it sound like L3 switching is directly dependent on VLANs, and I just didn't
see it - it wasn't something I was just willing to accept.
Further more, the book states that VLANs allow for physical location
independence, but is also says that VLANs should not cross the core - those
2 statements seem partly contradictory to me.
Here is a summary of how I see VLANs now.
Layer 3 switching is possible without VLANs (however the opposite is not
true. Well at least not without some form of Layer 3 intervention.)
VLANs simply the administration behind Layer 3 switching design.
Physical location (port location) independence is ok in front of the
layer 3 switch that is the the hosts gateway. Up to the hosts distribution
switch.
VLANs extending beyond the distribution layer switch across the core is
generally not a good idea - possible, but not recommended. This is the "flat
earth" design that Priscilla mentioned - VLANs that extend across the entire
internetwork.
Thanks!
Stephen Hoover
Dallas, Texas
----- Original Message -----
From: "Priscilla Oppenheimer"
To:
Sent: Monday, February 17, 2003 7:04 PM
Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
> This might help. What does the V stand for in VLAN? Virtual. VLANs are a
> method for emulating Real LANs in a switched network. The original poster
> seems disillusioned with VLANs. Well, I am too. :-) You can't do much with
> them that you can't do with a bunch of Real LANs connected by routers.
>
> Better come up with a way to emulate LAN and IP subnet benefits on a
> switched networks. OK, let's invent VLANs!
>
> But how do the VLANs talk to each other? Oh dear, we better go back to
> routers. Nah, still too slow, though it will work in a pinch. I know! We
> could speed them up and call them L3 switches.
>
>
> One last rather serious comment. This is not a comment on the newbiness of
> the original poster, but I must say that I think it is common for newbies
to
> get confused by VLANs.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=63210&t=63147
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