2960X stack ring speed at 20G?

[m.yost]

I just received my first shipment of 2960X's and am noticing the stack ring speed isn't showing what I would expect.  I have (6)

WS-C2960X-48LPD-L in a stack.  There are no 2960S' in the stack where it would get downgraded.  Here is the output from a few commands...I would expect the Stack Ring Speed to be 80Gbps and the protocol to be FlexStack-Plus.

Switch#sh sw stack-ring speed

Stack Ring Speed        : 20G

Stack Ring Configuration: Full

Stack Ring Protocol     : FlexStack

Switch#sh sw det

Switch/Stack Mac Address : 7c95.f3ef.1300

                                           H/W   Current

Switch#  Role   Mac Address     Priority Version  State

----------------------------------------------------------

*1       Master 7c95.f3ef.1300     15     4       Ready              

2       Member 5017.fff0.d880     13     4       Ready              

3       Member e8ed.f3b3.3880     11     4       Ready              

4       Member 5017.ff41.e200     9      4       Ready              

5       Member 5017.fff0.eb80     7      4       Ready              

6       Member e8ed.f3b3.3600     5      4       Ready              

         Stack Port Status             Neighbors    

Switch#  Port 1     Port 2           Port 1   Port 2

--------------------------------------------------------

  1        Ok         Ok                6        2

  2        Ok         Ok                1        3

  3        Ok         Ok                2        4

  4        Ok         Ok                3        5

  5        Ok         Ok                4        6

  6        Ok         Ok                5        1

[Marvin Rhoads]

20 Gbps is the correct port speed for a homogeneous 2960X stack. Reference.

The 80 Gbps number from the data sheets is "bandwidth" figured in Cisco's marketing way - two rings full duplex means the bandwidth is 4x the port speed.

[m.yost]

Thats why my pre-sales guy and I figured it was.  Marketing speak.  You would think that they would say in the show commands that the protocol is actually FlexStack-Plus though!

[Marvin Rhoads]

I can't find the presentation right now but there was a similar one on the 3850 that I remember explaining how they came up with the numbers they use to market the stack speed. Probably a partner deep dive session.

Yes, I agree the show command should indicate the "Plus". Maybe you can get the TAC to accept the discrepancy as a cosmetic bug.

Edit - look at BRKARC-3448 on CiscoLive365 re the 3850. Slides 38, 86 and 91 shows how a 40 Gbps port speed translates to "480 Gbps" stack speed. (3 rings eastbound plus 3 rings westbound x 2 due to spatial reuse). I believe the 2960 is similar but with with a single ring eastbound and westbound x 2 for spatial reuse.

Message was edited by: Marvin Rhoads