Stackwise virtual link not working

[A_Marquez]

I've been trying to create a stackwise virtual link between a couple of C9500-48Y4C switches. I've configured the stackwise virtual domain on both switches and configured the interfaces that we're going to use for the link. Reloaded the switches but they continue to act independent of each other. 

Stackwise config on switch 1:

Stackwise Virtual Configuration:
--------------------------------
Stackwise Virtual : Enabled
Domain Number : 3

Switch Stackwise Virtual Link Ports
------ ---------------------- ------
1 1 TwentyFiveGigE1/0/48

Link status shows as D and Protocol Status as S

Switch 2

Stackwise Virtual Configuration:
--------------------------------
Stackwise Virtual : Enabled
Domain Number : 3

Switch Stackwise Virtual Link Ports
------ ---------------------- ------
2 1 TwentyFiveGigE2/0/48

Same Link Status and Protocol Status as Switch 1.

Both switches are running version 16.12.4 as well. 

Right now the switches are connected by a 1Gig SFP as I'm setting them up. We also have a 40Gig QSFP+ DAC that I had used first to try and set up the connection on a Hundred gig interface with the same results. Is there something else I'm missing?

[A_Marquez]

It makes sense to me now why stackwise wasn't working on the 1Gig SFPs as stackwise-virtual is only supported on 10G and up so I switched to using a 10G DAC cable. This has yielded better results as now the second switch in the stack attempts to reboot for the stack merge but once it gets done it repeats the process all over again with this message appearing  "Reloading due to reason stack merge" however now it's in an endless loop of reloading for the "stack merge". 

[marce1000]

   - Are there any additional informational messages on the console when this happens ?

 M.

[A_Marquez]

No, generally when the reload happens it's right after I'm able to log in to switch but there's not really a warning for when it will happen. However, I think I may have found the cause. We were trying to use a third-party QSFP+ DAC cable for the stackwise link. According to these release notes there wasn't hardware support for DAC cables prior to 17.2.1: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/17-2/release_notes/ol-17-2-9500.html

I upgraded to 17.3.1 from 16.12.4 but the cable I'm using still isn't being recognized it at all (it's a tripplite N282-01M-BK, supposed to be compatible with QSFP-H40G-CU1M) However, when I use a SFP-10G-AOC3M cable the stackwise virtual link works and the switches are stacked properly. 

[paul driver]

Hello
Possible bug - 

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvq56135