Nexus 9K and a QSFP to SFP+ breakout cable

[CiscoMedMed]

I wanted to be able to use the QSFP ports on my pair of Nexus 9Ks. And I noticed that there is such a thing as a breakout cable - 40Gbps on one side and 10Gbps on the other. My question is: how does the Nexus 9k deal with it when a breakout cable is attached to it? Would say interface Ethernet 1/51 become Ethernet 1/51/1 /2 /3 and /4? Thank you for any insight. 

https://www.amazon.com/40G-QSFP-4xSFP-Breakout-QSFP-4SFP10G-CU3M/dp/B00SIXC40U/ref=sr_1_7_sspa?dchild=1&keywords=QSFP+to+SFP%2FSFP%2B&qid=1621377896&s=electronics&sr=1-7-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE3Rk1ZREdEUEJEVFgmZW5jcnlwdGVkSWQ9QTA...

[Muhammad Awais Khan · Accepted solution]

Hi,

If you want to breakout 40G into 10G then yes it is possible with multiple options and you will see interfaces similar to what you mentioned

For example, if you configure module level breakout, the "interface breakout" command splits the high bandwidth 40G interface of a module into four 10G interfaces. The module is reloaded and the configuration for the interface is removed when the command is executed.

The following is an example of the command:

switch# configure terminal
switch(config)# interface breakout module 1  

You can also configure per port level break out instead of module if you want to keep one port 40G and other to be splitted into four:

interface breakout module 1 port 1 map 10g-4x

you can find more details at below link:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/interfaces/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide_7x/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide_7x_chapter_010....

[CiscoMedMed]

That is very helpful. Thank you!

[CiscoMedMed]

That's a huge help. Thank you!

[Muhammad Awais Khan]

you are welcome. Feel free to comment again if you face any issue or need further clarification  

[BrianSekleckiGE]

Apparently the N9K-C9372 / 9k 9372 onboard 40G module contains "NS ASIC (ALE)"; these modules have hardware / software limitations and cannot be used with break-out/breakout cables (4x 10g)
No matter what [ https://tmgmatrix.cisco.com/ ] says about [ N9K-C9372 ] and [ QSFP-4SFP10G-CU3M ]

Refer to:
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/ale_ports/b_Limitations_for_ALE_Uplink_Ports_on_Cisco_Nexus_9000_Series_Switches.html

"Breakout is not supported on ALE 40G uplink ports."
"The 40 Gigabit ports on the uplink module do not support the break-out mode of four 10 Gigabit Ethernet ports, but they can be converted to a single 10 Gigabit Ethernet port with the QSFP-to-SFP adapter (QSA)."