Measuring StackWise backplane performance

[Aurecon Group]

Hi all,

I have a stack of 4 x 3750-E switches that have been fully populated with 10Gbps X2 fibre modules for 10Gbps SAN connectivity.  I want to know if there is a bottleneck on the backplane of the stack, either on the individual switch's backplane or on the StackWise backplane.

Are there any ways to measure the performance using SNMP or otherwise?  Can I measure any drops/losses?  What are the bandwidth limitations of this backplane?

Thanks.

[Leo Laohoo]

What are the bandwidth limitations of this backplane?

Command:  sh switch stack-ring speed

[Reza Sharifi]

Hi,

Have a look at table-2 and also table-8 in this link:

here are the numbers from the data sheet:

• 160-Gbps switching fabric capacity

• Stack-forwarding rate of 95 Mpps for 64-byte packets

• Forwarding rate:

• 3750E-24TD-65.5 Mpps

• 3750E-24PD-65.5 Mpps

• 3750E-48TD-101.2 Mpps

• 3750E-48PD-101.2 Mpps

• 3750E-48PD-F-101.2 Mpps

• Memory:

• 256 MB DRAM and 64 MB FLASH

• Feature resources:

• 1005 VLANs

• 4K VLAN IDs

• 1000 switched virtual interfaces (SVIs)

• 468 routed ports per stack

• 9216 byte jumbo frames

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps7077/product_data_sheet0900aecd805bbe67.html

HTH

[Joseph W. Doherty]

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Posting

Can I measure any drops/losses?

They might show up under the ASIC stats.

What are the bandwidth limitations of this backplane?

Each individual switch has 160 Gbps fabric; unlikely you'll bottleneck there.

The StackWise Plus ring is "64 Gbps", which I believe is really dual 16 Gbps (duplex).  It's possible you can exceed the ring's bandwidth, especially between a pair of switch members, but if the bulk of your traffic is between 10g ports, dual 10g on one switch member would likely bottleneck before the ring itself does.