business case for stacking switches

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Mar 20th, 2009
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Hi all, we are in process of putting in a new lan,

the edge switches will comprise of 2960's or 2975.

In our partner company in Germany they have switches in closets, all with 1 invdividual connection to a core switch, in the UK we currently have other vendors stacked switches with 2 links to the core, 1 being redundant, the arguement is that they do not want to pay for the extra cost for the 2975 over the 2960. I think it is better to stack them as there will be only 1 redundant link needed per stack and this will save less more density on the core etc. most of our switch stacks are between 4 and 6 switches.


can anyone help with this arguement?


cheers


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Joseph W. Doherty Fri, 03/20/2009 - 04:55
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From a cost standpoint, if each switch has it's own dual uplinks, vs. a stack with dual uplinks, you'll need more ports at the distribution level, more cabling between the closet. If you're using copper for the uplinks, both the additional ports and cable runs are likely less expensive than the cost of the more expensive switches. If using fiber, beside the additional cost of the cabling and distribution ports, there's also the additional cost of the fiber connectors (e.g SFPs).


From a performance standpoint, the 2975 provides much higher bandwidth between stack members. This could be important difference if the closet hosts use gig and there's much traffic between hosts within the same closet. (BTW, the client port speed is important, 2975 provide 3x speed ports, but 2960s can be had with 2x speed ports. Assume choice is between 2960s with 3x speed ports too.)


There's a system management consideration, "one" closet switch to manage and monitor vs. multiple switches per closet (alough "clustering" is an alternative).


There's also VLAN management issues. Too complex to address here, but a single (virtual) switch per closet might be better when dealing with VLANs.

carl_townshend Fri, 03/20/2009 - 05:06
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hi there, thanks for the reply, can you please clarify what you mean by speed ports ?

Mohamad Qayoom Fri, 03/20/2009 - 06:47
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How many ports are they going to use? Is there any chance of growth? Can your client afford downtime?

Joseph W. Doherty Fri, 03/20/2009 - 07:15
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2x speed = 10/100 Mbps

3x speed = 10/100/1000 Mbps

jeff.cook@wecu.com Fri, 03/20/2009 - 08:23
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If you stack the switches and use etherchannel to the core, then you get both redundant connection and increased bandwidth to the core. You would also have less connection needed at the core. Depending on how may switches in the stack at most you would need 1 per switch. Let's say you have six switches in the stack. Then maybe you only need/want 4 links to the core (not 12). This would save a possible needed upgrade to the core.


This all is based of the assumption your core is stacked.

Leo Laohoo Sun, 03/22/2009 - 17:47
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One thing to add about 2960 vs 2975. The 2975 comes in one flavour: 48-port with 24-port PoE.


The question is: Do you want a PoE switch?


If the answer is no, then get the 2960 and use the "clustering" feature. Using this feature is it possible to "manage" a number of switches by using ONE IP Address (http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_46_se/command/reference/cli1.html#wp8476083).


It is really hard to enforce a one-ring-to-rule-them-all because each regional IT manager want the network to be set up to their specific standards to meet their specific needs. I guess you just have to roll with the punches.



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