3750 v 3750 E Series

Unanswered Question
May 3rd, 2009

I have a simple question that I can not find a direct answer to. In a stand alone configuration does the 3750 E have a faster backplane than the 3750? The 3750 has a 32 Gb/s backplane which for a 48 port switch is oversubscribed. what is the (non stacked) backplane of a 3750 E.

Please don't reply that I should use the 3560 in such a situation.


I have this problem too.
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thotsaphon Sun, 05/03/2009 - 10:14


Please check out this link:

Cisco Catalyst 3750-E Series Key Features

• StackWise Plus for ease of use and resiliency with up to 64 Gbps of throughput


Edit : Sorry I missed reading the whole question.


WS-C3750E :

160-Gbps wire rate, nonblocking switching fabric capacity



Joseph W. Doherty Sun, 05/03/2009 - 10:34

3750-E (and 3650-E) backplane's bandwidth is also documented at 128 Gbps. (Also 48 port models are rated at 101.2 Mpps.)

BTW, non-oversubscribed would require 136 Gbps for 48 gig ports and dual 10 gig (as found on the 4948-10GE).

Jon Marshall Sun, 05/03/2009 - 10:39


3750-E datasheet states that switching fabric capacity is 160Gbps which would mean based on your figures that the 3750-E 48 gig port switch is not oversubscribed ?


Joseph W. Doherty Sun, 05/03/2009 - 10:45

Jon, if 3750-E does have 160-Gbps fabric bandwidth, it wouldn't be oversubscribed. However, if you search Cisco's site, you'll find other documentation that notes the 3560-E/3750-E fabric bandwidth is 128 Gbps. (More fun, Cisco's switch guide notes fabric as 64 Gbps.)

Since some documentation lists switch as wire rate capable, I would lean toward a fabric of 160 Gbps.

thotsaphon Sun, 05/03/2009 - 10:50


So we sometime need to find the correct document outside cisco world. J/K (grin)


Jon Marshall Sun, 05/03/2009 - 10:56

Or, we take all the different figures, add them up and divide by the number of figures to get an average :-)

Jon Marshall Sun, 05/03/2009 - 10:55

Yes, had this problem before with conflicting documentation on the 6500 switches.

I think 64Gbps is the connection between 3750-E switches in a stack rather than the actual switch fabric per switch so you could argue in a stack it is definitely not wire rate if all ports in one switch were talking to all ports in another switch in the same stack.

As fo 128Gbps - pass, i haven't a clue where that figure comes from :-)


thotsaphon Sun, 05/03/2009 - 10:58


I have to agree with you on what we have to to do is "Average".

5P! I love that clue. (grin)


Joseph W. Doherty Sun, 05/03/2009 - 11:05

128 Gbps, see attachments.

64 Gbps fabric, see http://www.cisco.com/en/US/prod/switches/ps5718/ps708/networking_solutions_products_genericcontent0900aecd805f0955.pdf, pages 108 and 109.

BTW, so far I've only found the 160 Gbps reference with regard to the 3750-E. I wonder if this is some additional bandwidth for Stackwise+, although its only an additional 32 Gbps not 64 Gbps.



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