Cable labels feel unnecessary while every connection is visible and fresh in memory. They become valuable when the rack is dark, a switch has failed, or one of three identical power supplies must be disconnected without touching the others.
Label both ends. A label at the switch helps identify the destination; a label behind the device helps find the correct switch port. Use durable printed text, not color alone, and keep names short enough to read without rotating the rack.
Describe endpoints rather than temporary intentions. pve-a / nic1 and
sw-a / 08 remain useful after a VLAN change. “Server cable” does not. Power
leads should identify the device and power-supply input, especially when dual
supplies connect to different distribution units.
Make the physical labels agree with the network inventory. When moving a cable, update both immediately; a confidently wrong label is worse than none. A quick photo after a clean change provides additional context, but it should not be the only record because ports and text may be hidden.
Leave a small service loop where space permits and avoid placing labels where they block a latch or fan. Retire old labels completely instead of crossing them out: during an outage, two competing answers slow down the safest action.
This is inexpensive operational tooling. Ten quiet minutes with a label printer can remove uncertainty from the exact maintenance window in which careful, reversible actions matter most. Do it early.