Two cisco 3750X stacking together

[vd123_cisco]

Hello All,

Could someone please confirm if we can stack the two 3750x switches together as the following -

Will this also provide 32 stack ring speed?

Thank you in advance.

Kind regards,

Jay

[Leo Laohoo · Accepted solution]

No.  "X" them.

[Marvin Rhoads · Accepted solution]

...and when correctly cabled as Leo noted, the theoretical Stackwise Plus maximum bandwidth is 64 Gbps if you're using 3750X's. (32 Gbps is for the older StackWise technology on the non-E and non-X 3750).

Lots of details in this Cisco Live presentation and this whitepaper.

[vd123_cisco]

Hi Leo,

Thank you for the reply.

could you please explain what issues can occur if they are not 'X 'connected

Would it cause only one stack port on each switch to be up and the other to be down?

The reason I am asking this is becuse I have got a switch which stacked in this manner at the remote location and I can see that stack port 2 on both the switches are in down state.

Can it be a faulty cable?

Thanks

Jay

[Leo Laohoo]

could you please explain what issues can occur if they are not 'X 'connected

One side is "out" and the other side is "in".  So you've connected both "in" together and both "out".

Besides, Cisco's documentation recommends the cables to be crossed.  Why re-inventing the wheel?

[vd123_cisco]

Thanks Leo

[Leo Laohoo]

Thanks for rating our posts, Jay.

[Seb Rupik]

Hi Leo,

It was my understanding that you must cable to ports the make a continuous ring.I wasn't aware of in/out ports.

I have seen the following stackwise cable layout in production:

...and working at full 32G (it was a mixed G and X stack).

cheers,

Seb.

[Leo Laohoo]

Seb,

What you have is fine, because you are "X" or crossing them (even though the first and last are straight down).  Take two and do what the OP did, from what I learnt long time ago, it won't work. 

[Syed Aman Hussain]

Hi vidi,

make the two switches in X connection it will give you full bandwidth will full stack speed

[Joseph W. Doherty]

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Posting

My understanding, yes you can connect two units like that.  I.e. how the ring is connected doesn't really matter, except perhaps for visual neatness.

Issue this command:

3750X#sh switch stack-ring speed

Stack Ring Speed        : 32G

Stack Ring Configuration: Full

Stack Ring Protocol     : StackWisePlus

And you're good if you have the 32G (duplex) and "Full" (regardless of "X" connected or "vertically" connected).

As noted by another poster, the 3750-X provides 64 Gbps stack bandwidth (I believe StackWisePlus ports to be 16 Gbps, duplex).

[vd123_cisco]

Hi Josheph,

Thank you for the reply. The reason I asked that question is because i saw stack port 2 on both the switches in down state.

         Stack Port Status               Neighbors

Switch#  Port 1     Port 2           Port 1   Port 2

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

  1        Ok            Down               2      None

  2        Ok            Down               1      None

So I was wondering if this kind of stacking topology would cause it. The stack is operating in 16G.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Have you tried reseating the down stack port connectors?  What does show switch stack-ports summary reveal?

BTW, if you look here: http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/hardware/quick/guide/3750GSG3.html#wp53466 or

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/hardware/installation/guide/HIGINSTL.html#wp1151552. You'll see different ways of connecting the same units.  Note how sometimes stack ports 1 or 2 connect to another stack port 1 or 2, i.e. they are not always cross connected.

[mahesh18]

Hi Joseph,

I have similar issue here where 2 stack switches are connected via single cable and it is not crossed.

As it is in production so i can not cross them.

I added second cable it still shows down down.

sh switch neighbors

  Switch #    Port 1       Port 2

  --------    ------       ------

      1         2            None

      2         1            None

         Stack Port Status             Neighbors

Switch#  Port 1     Port 2           Port 1   Port 2

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

  1        Ok        Down               2      None

  2        Ok        Down               1      None

#sh switch stack-ports summary

Switch#/  Stack   Neighbor   Cable    Link   Link   Sync      #         In
Port#     Port              Length    OK   Active   OK    Changes   Loopback
          Status                                          To LinkOK
--------  ------  --------  --------  ----  ------  ----  ---------  --------
  1/1     OK         2      50 cm     Yes    Yes    Yes        1        No
  1/2     Down      None    50 cm     No     No     No         0        No
  2/1     OK         1      50 cm     Yes    Yes    Yes        1        No
  2/2     Down      None    50 cm     No     No     No         0        No

So by default when they are not crossed even though both cables are connected only one  link will be up up at one time?

Regards

MAhesh