[TriLUG] OT - gigabit switches

[Ryan Leathers]

I would expect a lab environment to make tremendous use of VLANs.  I
would also expect that you'd have reason to communicate between VLANs.
In the case where your load testing would include multiple VLANs, you'd
want a layer 3 switch.  Using an external device for L3 decisions would
be sub-par at best and likely not acceptable at all in an inter-VLAN
load testing scenario.  You'll also want to be sure the L3 switch has
the ability to rewrite frame headers without performing L3 lookups on
every Packet. Cisco implements this as CEF these days and its a feature
of even the lowliest L3 switch they make.  

Now on the other hand, if you are pretty sure you don't need VLANs then
just make sure you have a L2 switch backbone capable of non-blocking
throughput rates at least equal to the number of hosts that will be in
use at one time and you'll be fine.



On Wed, 2006-09-20 at 14:23 -0400, Christopher L Merrill wrote:
> We would like to upgrade our testlab to a gigabit switch.  I'm not an
> expert in this area (I spend most of my time at level 7). Maybe some of
> you network gurus can set me straight.
> 
> In our lab we'll have 10-25 machines (some with dual NICs) mostly fast
> ethernet but we're moving machines to GigE. We currently have a Dell 2324
> with 2 GigE ports.  Performance between the machines connected directly
> to the switch is the only real goal.  Management functions are not
> important, beyond the desire for simple plug-n-play management that we
> have today (in other words...no management - just plug them in).  Note
> that we do load-testing in the lab, so for a network with only a handful
> of machines, they run a LOT of traffic between them - frequently to the
> CPU/NIC limit of each machine.
> 
> I've read a little on layer-2 and layer-3 switches and think I grasp the
> differences, but it is not clear to me if there would be any performance
> benefit for US with a layer-3 switch.  Budget is obviously a concern so
> a $2000 switch will take some selling.  Under what kind of situations would
> we see a difference in the total throughput rates on, for example, a Dell
> 2724 (layer 2, <$300), a Dell 5324 (layer 2/3, $750) and a 6024 (layer 3,
> $2000)???  What about an older Dell 5224 (layer2/3, ebay $300)?  What does
> "layer 2/3" mean?
> 
> Any recommendations or pointers for some good reading would be much
> appreciated.
> 
> p.s. We have lots of Linux boxes in the lab  :>
> 
> TIA,
> C
> 
> 
> 
> -- 
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> Chris Merrill                           |  Web Performance, Inc.
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