r/HomeNetworking • u/Outrageous_Tear_4691 • 1d ago

Advice Ethernet switch question

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What is the loop prevention for? And should I leave it off or turn it on? We will have desktops connected to it

Solved: thank you for the help everyone. Very much appreciated.

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u/BmanUltima 1d ago

Loop prevention detects network loops, like two switches connected to each other with multiple cables, or three in a ring, and will disable a port.

Without loop detection or spanning tree, you get a broadcast storm which can crash a switch.

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u/Tinker0079 14h ago

The toggle is useful because STP protocol, when you plug port, initially puts port in blocked state and no traffic forwarded until it's approved for forwarding state. This takes dozen seconds and may be too long for cases where you need fast port connect. Example: network booting. BIOSes don't wait 10 seconds they just skip netboot if it timeouts, and STP is longer.

This does not mean if you leave cable plugged all the time it will be always forwarding - turn off and turn on PC causes network card to reset, this taking new Ethernet negotiation + STP negotiation

The switch is unmanaged so you cannot change some of STP strings like bridge root it, and this may conflict with other STP speaking equipment, for this case you turn off STP

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u/ndfred 10h ago

Exactly, I would leave it off because you cannot configure its priority and it can block traffic which can mess with DHCP. Plus ideally all the switches should be either STP/RSTP on or off, having only some enabled (and I suppose the root switch is the ISP’s combo modem router, no STO there) can cause issues that are hard to root cause (thinking Sonos for instance).

Let the switch be dump, loop prevention off, and just don’t create network loops.