C3750X-24S-E as core in a L2 network

Unanswered Question
Nov 25th, 2011

Hello all,

I want to deploy the C3750X 24-port SFP switch as the core switch in a large Layer 2 switching domain.

The switch will need to run:

+/- only 10 large VLANs, 6 VLANs with HSRP

+/- 500 MACs total

+/- 5 OSPF sessions default timers

standard PVST+ (no Rapid PVST+)

i need around 27 SFP ports (24 + 4 on network module=28=ok, extra capacity by stacking)

Looking at the switching capacity of the specs (160 Gbps) this is much better than a C6500 with SUP32-GE !

Will it be able to handle this or should i look for C6500+SUP32GE or C6500-SUP720 or maybe even C4500 ?



I have this problem too.
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Leo Laohoo Fri, 11/25/2011 - 18:51

Hi GN,

Firstly, have you ever considered redundancy?  I mean you put your "faith" in a single 3750X-24S to act as a core/distro.  What happens when this unit fails?

I mean i'd consider getting two and stacking them together (if the funds are available).

Next, the 6500.  The Sup32 ain't designed for a core/distro or even a mini-/lite- core or distro.  The Sup32 is commonly used a an access switch.  The 6500 with Sup720 and 6724-SFP blade is what you are looking for. 

gnijs Sat, 11/26/2011 - 15:44

Sorry i didn't mention it, but of course, i am foreseeing two C3750X (not stacked because they are in two different rooms) but just L2 connected with a portchannel, thats the reason why i mention HSRP by the way).

Ok, i agree i can forget the 32G (it has a shared bus of 32 Gbps). I know my alternative is SUP720 with 6724SFP. But have you looked at the price difference ?



Leo Laohoo Sat, 11/26/2011 - 15:59
But have you looked at the price difference ?

This really depends on what you are trying to do.  I have no idea what your work practices are but in IT projects, I always tell the clients this:  In IT projects, you have three ways of doing things, correctly, cheaply and quickly.  Now choose TWO.

Back to your issue.  If you want to use Sup 32, then it's up to you.  But the question I'd like to ask you is this:  What blade do you want to use to terminate 24 SFP ports?  If you're going to say "a WS-X6724-SFP" then my rebuttal will be "Sup32 won't support this card".

Sorry i didn't mention it, but of course, i am foreseeing two C3750X (not stacked because they are in two different rooms) but just L2 connected with a portchannel, thats the reason why i mention HSRP by the way).

Might become a tad bit complicated if you put two stacks in different locations, connect them together with EtherChannel BUT you connect server (configured as etherchannel) to the two stacks.  Not ideal.

gnijs Sat, 11/26/2011 - 16:34

The IT project thing, that is a classic. No i was think to use 2x GBIC linecards with the SUP32. Actually the current connections are all GBIC and using a GBIC card would prevent me from buying new SC-LC fiber patch cables and SFP tranceivers :-)

gnijs Sun, 11/27/2011 - 09:52

1 Gig is enough, worst-case we can make a channel 2x 1 gig

gnijs Wed, 11/30/2011 - 08:32

We have gone for the C3750X. SUP32 has only one supported fiber linecard left, and that is the 16-port GBIC module. Can't insert any SFP card without also upgrading to SUP720, which gives as more performance than needed. Maybe SUP32 becomes EOL next year or shortly also. Don't want to risk that. Hopefully, the C3750X can support 28 SFP interfaces all connected, 11 L2 VLANs, 5 L3 SVI VLANs, 500 MACs, 4 OSPF with default timers, 20-30 broadcasts pkts in total per second on sum of L3 vlans. 28 SFP interfaces running average of 5 VLANs = 140 logical STP interfaces running PVST+, Should be able to handle that. Raw switching performance is even better than SUP32...

Joseph W. Doherty Wed, 11/30/2011 - 09:29


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Besides using a port channel between your two 3750Xs, you might consider using a 10 gig link if you can afford the upgraded module.  You also might consider eventually moving the two 3750Xs together so you can take advantage of their stacking feature.


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