Re: 3750s in the Core

IMO the 4948 is a happy middle ground for this - a 4500 style fabric
in a pizza box with some redundancy - one of my personal favorites. I
like to use these with the 10GB LRM's as opposed to the stacking
approach. I am not a huge fan of stacking in general, but that's just
me. I have seen network architects often stack 3750's when a chassis-
based solution is inevitable (forecast_growth). I have seen other
situations where the 3750 stack was overkill or missed a key objective
(redundancy_requirement).

Ask yourself:
- what you are trying to do (features)
- how many things do you need to do it with (connections)
- and the level of risk acceptable for your particular implementation
(ACCEPTABLE_RISK!)

...the answer will come, budget permitting.

~M

On Jun 17, 2009, at 7:25 AM, Radioactive Frog wrote:

> Pavel, this is what I was going to write in my next posting. From
> enterprise and best practice point of view, I don't think there was
> any
> focus on this.
>
> Thanks for the clarification.
>
>
> On Wed, Jun 17, 2009 at 7:50 PM, Pavel Bykov <slidersv_at_gmail.com>
> wrote:
>
>> 4500 a NON-IOS switch?
>> 3750s that don't fail?
>> Core/distribution/access model when there is just a stack of 3750s?
>> AVERAGE loads?
>> Oversubscribtion quite low?
>> ...
>> I can't believe I'm hearing all this...
>>
>> 1. 4500 is a chasis with connectors. It's pretty dumb actually. What
>> controls the switch is the SUPERVISOR. So when you're looking at
>> 4500, look
>> at SUPs first. Price important? Try to price 240 1Gbps PoE ports with
>> routing capabilities. 3750s will be considerably more expensive
>> then 4506
>> with SUPV-10GE. And as for "4500" being a NON-IOS switch... well,
>> either
>> i'm
>> not understanding what does this means, or Ashan is way off. All sups
>> starting with III are perfectly able to run IOS. Newest SUP6 was
>> actually
>> never even able to run CATOS in the first place. And have you
>> checked the
>> discount on bundles, where you get free cards, PSs etc?
>>
>> 2. If you think that 3750 never fail, well maybe you haven't seen
>> enough of
>> them or under real load. I'm not talking about having ten 3750 with
>> insane
>> uptime - that's hit and miss. I'm talking about hundreds of them
>> under
>> different conditions. Try loading on them 12.1(19)ea1 and
>> connecting one
>> gigabit interface and one 10-mpbs interface. The whole stack will
>> fail in
>> due time, with an Ethernet controller error, making any forwarding/
>> failover
>> impossible with only solution to physically unplug the stack
>> master... TAC
>> team for 3750s is just as active as for other devices, and there
>> are quite
>> a
>> number of failures that bring down the whole stack instead of just
>> one
>> switch... And what about One PS, even when there is an RPS, it will
>> have
>> problems and you need to be aware of severe limitations, etc, etc.
>>
>> 3. Core/distribution/access models were designed as a guideline to
>> enable
>> bes HA and scalability, among other things. It is a model that solves
>> complex number of issues, and not just some guideline that you need
>> to buy
>> three switches instead of one. If you have just some LAN with
>> users, you
>> don't have to retrofit the design into that model. It's best
>> practice, and
>> creating something and then saying it is best practice because you
>> were
>> able
>> to retrofit it to the model is not how it works.
>>
>> http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/HA_campus_DG/hacampusdg.html
>>
>> 4. Joseph, average loads do not have to be the cause, but the
>> effect. Many
>> times i've seen that relatively low loads were quadruppled because of
>> network design improvement. Network never operates in average mode.
>> What is
>> it an average of? 30 seconds? 5 minutes? a year? a century? sure, i'm
>> exhaggerating here, but interface operation is a microsecond or
>> sub-microsecond matter. It's all bursty in nature, no matter how we
>> take
>> it,
>> because virtually no enterprise runs real-time operating systems. A
>> cop
>> does
>> not stop you on the street because your average speed for the past
>> week was
>> above 4mph, and it does not mean that roads should be designed for
>> such a
>> low speed. You need to get somewhere quickly, then stay there for a
>> while,
>> then get quickly somewhere else. Designing the network for average
>> loads is
>> like desiging roads for average speeds... It may seem ok in a
>> theory of
>> some
>> sort, but in practice the problems could be hiding behind every
>> corner.
>>
>> 5. Ryan, you mentioned oversubscription... of what to what and
>> where? 3750
>> has a lot of architectural limits. It can be oversubsribed as any
>> other if
>> ports are not connected correctly evenly to port-asics and could be
>> ovesubscribed without any problem. When it's a stack than all
>> oversubscription naturally grows.
>>
>>
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Received on Wed Jun 17 2009 - 08:02:32 ART