Hi @DR1 I had the case last year, we set up a remote stacking between MS425 using MA-QSFP-40G-CSR4 and MPO12 Some former topics say that this is not supported by Meraki but here the details provided by my Cisco Solution engineer implying it is supported as their DAC / Stack cables are standard. SR4 and CSR4 are both MPO interfaces.
My recommendation would be that you will be ok with the MPO12
The document shows this but
Channel Pairs (Ethernet link Tx and Rx):
1 and 12 (Tx1 and Rx1)
2 and 11 (Tx2 and Rx2)
3 and 10 (Tx3 and Rx3)
4 and 9 (Tx4 and Rx4)
Channels 5, 6, 7 and 8 are unused I drafted quick specs after ends based on this first experience To note, I didn't follow up this project from start to end but they follow my initial recommendations and it ends up working fine. Cisco Spec slide about their QSFP-40G-SR I hope it helps. I'm pretty sure the same could be done with QSFP28. A similar discussion from last week https://community.meraki.com/t5/Managed-Services/MS355-long-distance-stacking/m-p/102794#M392 If you have access to a Cisco Solution engineer, you may ask him the fiber breakout specifications for MA-CBL-100G / 100GQSFP28 https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/data_sheet_c78-660083.html https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/datasheet-c78-736282.html https://meraki.cisco.com/lib/pdf/meraki_datasheet_sfp.pdf Edit: To confirm, MS425 Stack ports have been set to "stacking" so technically no different than a stack dedicated port on other series.
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