@KevinC how far apart are the two switches? If they are close together then the options are: CAT6A patch cable - up to 10Gb/s with third party Cu SFP+ modules MA-CBL-TA-1/3M - 10Gb/s and supported if you have SFP+ sockets on the MS390 MA-CBL-40G-50CM/1M/3M - 40Gb/s and supported if you have QSFP+ sockets on the MS390 If they are further apart then you simply use transceivers and OM3/4 fibre patch cables. All the supported options are found here: https://meraki.cisco.com/lib/pdf/meraki_datasheet_sfp.pdf
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