Dear Sender
Thank you for raising your questions, hope my answer could help.
There're a few ways to identify whether the ports is L1 down or L2 down.
If you're checking the status of port from GUI then this few method would help you identify.
a. If you want to check the summary of interface status.
Go to Fabric > Inventory >[pod] > [node] > Interfaces > Physical Interfaces, you will get the full picture of port status on the right side. 
b. Go to Fabric > Inventory >[pod] > [node] > Interfaces > Physical Interfaces > eth x/y
Here you could see Oper Stat & Oper State Reason listed on the right side for dedicated port. For example:
c. Still on the same place, Go to Fabric > Inventory >[pod] > [node] > Interfaces > Physical Interfaces > eth x/y , right click on the name of the interface and choose open in Object Store Browser.
Seach for ethpmPhysIf and move down there's a line named operStQual also describes the reason of link failure.
d. Login to the device, you'll also get the log for reason of link failure, like config change, adminstrative down, sfp missing, no lacp pdu, etc.
If you want to get one or other ports detailed status through API, please check the one below:
Node Port Status
<ip -address>/api/node/class/topology/pod-1/node-101/ethpmPhysIf.json
“operStQual” mapping to the “Oper State Reason” and:
"operStQual": "none" means “connected”.
"operStQual": "link-failure" means “notconnect”.
"operStQual": "admin-down"
"operStQual": "sfp-missing"
"operStQual": "suspended-due-to-no-lacp-pdus"
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