3750 Stackwise Technology Question

[reynaldob]

Hi all,

I do have a question regarding the backplane capability of the 3750 switch. I know from the CCO docs that it has 32 GBps backplane capability. My question is as the stack increases, does this mean that it still has the same 32 GBps backplane bandwith? Or is the bandwith divided on the number of switches that are being stacked?

My assessment would be that if the stacked switches would be considered as 1 switch, I would assume that all the links would still have 32 GBps backplane capability. Am I right?

I need a CCO doc that I could show my client, they are planning to convert a 3750 pairing stack:

Core Sw ------------ 3750

| ||

|--------------- 3750

to:

Core Switch -------- 3750

| ||

| 3750

| ||

|-------------- 3750

They are converting to save the ports.

Is this design the same as the first one Backplanewise? Does this mean this would not decrease the bandwith capability of the switches? Does this mean also that this design is the same as the previous one?

Thank you very much gurus!

Best regards,

Bobet

[#2]

This link will be usefull for u,check this out

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00801cc828.shtml

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a00801a6558.html

[johgill]

Bobet,

I cannot tell exactly what your diagrams look like as the spacing got a bit messed up.

I can tell you that the backplane is extended with the stackwise connections. The 32Gbps backplane is in a ring topology on the inside, so when you add the cables on the exterior, they are directly interfacing with the backplane. You are sharing that same backplane with all switches in the stack on the stackwise cables. Remember that is 32Gbps full-duplex, so it is really what you may consider 16Gbps.

[7rbowenii]

I have thoroughly tested the 3750 architecture at Cisco's Customer Proof of Concept Lab in NC. The 3750 stack is capable of 32 Gb of throughput (30-ish with overhead.) However, you have to understand what throughput really means. The 3750 is capable of advertised throughput if you use oversized (9KB packets). However, the maximum forwarding rate for a 3750 is 15million pps @ 64B packets. So, 15 million x 64 X 8 = 7.68Gbps throughput. So, I would be careful how you ask as well as answer the question. i would also be sure to test the switches stacking capabilities thoroughly before I would recommend them. There seem to be some cabling difficulties as well as some poor error reporting of stack members failures.

[reynaldob]

Hi all,

Thank you for the insights. I guess that the BP always gets divided once the stack increases.

Again cheers all!

[reynaldob]

Hi...

I would like to know how did you get the formula?

15M (that I know) x 64 (64 bytes max?) x 8(octet? ports per asic?)

I hope you can still answer this and thanks for the reply it did give some light on the issue!

[7rbowenii]

Cisco states that the max PPS for the platform is 15 Million. When they measure max PPS, the use 64 byte packets, because you can pass the most packets per second with the smallest packet sizes. there are 8bits in a byte. So, the equation 15 Mppsx 64 bytes * 8 bits per pyte gives you your # of bits per second.

-Bo