Change Port Speed for Cisco C9500X-60L4D Switch

[vondoom2]

Good morning,

I have a Cisco Catalyst C9500X-60L4D switch and recently I have been trying to set the speed for a fiber QSFP interface.  Is there another command I should be using outside of the "speed <insert value>"? Auto negotiate does not appear to be working so as a test I wanted to actually set the speed parameter.  When I try to enter a value for the interface from configure mode it's not allowing me to and my searches have all shown me the same command so far.

[marce1000]

  - Normally if you attach a specific QSFP-type to the interface the speed is always fixed according to it's capabilities , 

 M.

[vondoom2]

We are using QSFP-DD transceivers from our switch and trying to communicate with a 200G transceiver inside a server.  I know QSFP-DD is capable of doing 400G, but the auto negotiate does not appear to allow it to scale to the speed of the lower transceiver so I wanted to try setting the speed myself, before having to go out and buy another transceiver.

[marce1000]

 - What is the exact type of the transceiver(s) you are trying to use ? 

 M.

[vondoom2]

The QFSP-DD in our switch is Cisco QSFP-DD for single mode fiber and the transceiver in the server is Proline MMA1L10-CR-PRO (100G single mode fiber).

[marce1000]

@vondoom2 wrote :     The QFSP-DD in our switch is Cisco QSFP-DD ....

  - That is not a complete description of the QSFP-DD full model , I think , checkout : https://tmgmatrix.cisco.com/?npid=5721
      which one do you have ?

 M.

[vondoom2]

Cisco QDD-400G-FR4-S is the QSFP-DD we have.

[marce1000]

 - Ok , if you look it up in https://tmgmatrix.cisco.com/?npid=5721 , then you can see that it has a fixed Data Rate , 
   so the speed can not be changed, there are only  few other models listed in the table with variable speeds.

 M.

[vondoom2]

So, am I unable to change the speed for that port because that transceiver has a fixed data rate?  I would think that I should still be able to put a speed configuration on any port I want. Removing that speed change would be easy enough.  Right now I have 10G ethernet SFPs as well that I am unable to change the speed on (just as an experiment).  And those I've connected to another switch/server/etc that had  a lower data rate like 1G.  I was able to ping between the two interfaces just at the speed of the lower interface.

[marce1000]

 - You could try to configure any speed that you want , but when a particular SFP model is inserted there is a 'cutoff' and the port will operate according to the specifications of the particular SFP model  , 

 M.

[vondoom2]

The problem I'm running in to is the "speed XXXX" command is not working for me, is there another command for changing the speed that I should be aware of, just to try it?

[vondoom2 · Accepted solution]

I was able to come up with the answer through a bit of experimentation on my own.  If you go into configure mode on any interface (the transceiver has to been ejected or not there) you can change the speed of that port.  However, I found that once you inserted a SFP/QSFP the fixed speed setting for that transceiver overrides that speed setting to the port.  Thank you very much for your assistance.

[RAdamWilliams]

Fiber transceivers (to my knowledge) don't negotiate speed. You have to match transceivers of the same speed and type on both ends of the link.

[vondoom2]

But I still should be able to enter a command to change the speed of any port I wish.  Right now I have copper SFPs in my switch that I am unable to change the speed on, just as an experiment.  If I have to buy a different type of QSFP then that's fine, but before I go that route I wanted to try changing the port speed before I go out buying different QSFP transceivers. From configure mode I can see "speed" and when I enter ? it gives me a list of speed values I can try changing to, but when I actually try to use the command 'speed XXXX' the command does not work.