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by Fnoord 6 hours ago
Still, it is useful to mention.

If PoE required: use copper twisted pair.

If both sides SFP+ (preferred, but not always possible):

Physical presence: DAC (very cheap).

Not physical presence (e.g. has to go through wall, floor, or longer distance): fiber (OM3 are very cheap but apparently the color being translucent is regarded as nice).

Else: copper twisted pair.

I've applied this on my (rental) house. One server has a 10 gbit copper twisted pair NIC because it also has a PCIe switch with M.2 storage on the same physical PCIe board. Two WLAN APs are powered by switch in fusebox. The Unifi Protect appliance is also powered by twisted pair copper. But I was also able to get an OM3 fiber through the same wall hole.

And always terminate at walls. So if a cable in house goes bad, the one through the wall or the socket is unaffected. Works with both fiber and twisted pair copper.

You can already notice it in this post. DAC barely is part of the content. It is fire and forget, no caveats, lowest latency and lowest power usage. So it tends to be forgotten, but a DAC cable is useful if both devices got physical (vicinity) presence. An alternative could be networking over TB.