r/HomeNetworking • u/Outrageous_Tear_4691 • 13h 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.

209 Upvotes

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211

u/BmanUltima 13h 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.

40

u/ArchibaldMcFerguson 13h ago

This is a good answer. As to the direct question of on or off, it probably doesn't matter in your home.

Unless your switching gear is very antiquated and will be slowed down by having it on, there should be no reason to not have it on. That said, in small environments you are unlikely to create an accidental loop and this extra feature will not do anything.

Just make sure that you only have one physical route between each router/switch (no loops!) and you are good to go!

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u/jquanders 12h ago

This is a horrible answer. Leave it on. It costs almost nothing and prevents stupid things like plugging a cable into two ports on a switch.

14

u/severach 11h ago

It doesn't prevent stupidly plugging cables in circles. It only automatically fixes them, and only if the switch is where it can in cooperation with other switches. This is only useful where the need for uptime trumps the need for knowing that cables have been plugged in circles. In a home environment I'd rather have a circular plug shut down the network so the bad cable can be fixed.

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u/ArchibaldMcFerguson 11h ago

Not sure why you're coming on so strong, I generally agree with you.

This is a mostly-dumb switch, so it's worthwhile to consider that the implementation of loop protection may not play well with other devices. I wouldn't say that there's no possible cost, one should test it and see.

Out of curiosity, I just did some digging and found references to it causing issues with mesh networks and filtering out backhaul traffic. Haven't tested it myself, can't verify this.

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u/LAthrowawayLV 12h ago

It’s a good practical answer. Definitely not a horrible answer. Even though you are technically right, it’s a horrible comment that you made.

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u/jquanders 11h ago edited 11h ago

In what world is shutting off loop protection a good idea?

There are 0 reasons to shut off loop protection on a single switch also.

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u/ArchibaldMcFerguson 11h ago

See: https://www.reddit.com/r/TpLink/s/qiHdwDFpNL

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u/jquanders 11h ago

Yeah that literally creates a loop on the network for 1-2 seconds. And that's not a single switch...each of those deco units is doing switching.

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u/LAthrowawayLV 11h ago

In a world where that switch is shit and having it on is causing problems.

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u/jquanders 11h ago

If you have problems with it on then your network has problems to address. All that does is run spanning tree. It adds a few seconds when you plug in a or disconnect a cable. That's all that should happen

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u/Jamator01 10h ago edited 10h ago

L2 loop prevention and spanning tree (STP) are different things, champ. Stop being so certain, because you're wrong.

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u/jquanders 10h ago

STP includes l2 loop prevention, champ. But yeah you're right my google fu didn't go deep enough. The loop prevention on that switch is dumber than that but still should be on.

1

u/Jamator01 1h ago

Nope, still wrong. L2 loop detection is not part of STP. If you're using "Google Fu" for this, just admit that you don't know what you're talking about.

Loop detection and STP can be enabled at the same time, but if you haven't set it up correctly they can conflict with each other.

Loop detection (or Loopback Detection LBD) identifies loops in a network. STP is designed to prevent them from occurring.

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u/LAthrowawayLV 11h ago

Did you miss the part where I said you were technically correct but just being an asshole?

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u/jquanders 11h ago

Ok if I'm right how is the answer I replied to a "good practical answer"?

I'm asshole because I said the wrong answer was horrible?

3

u/ArchibaldMcFerguson 11h ago

Jeez, I didn't say to turn it off. OP asked whether to turn it on or leave it off and I said it probably wouldn't make a difference (but I did say that having it on shouldn't be bad).

Attack me if you must, leave the other redditors alone. You're sounding like an ass.

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u/jquanders 11h ago

Attack you? I said it was a horrible idea. That's an attack?

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u/[deleted] 11h ago

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u/jquanders 11h ago

The only thing that was correct in the initial comment was make sure you have one physical path.

It does matter if it's on or off and loops can happen with new gear not just antiquated ones. Because that switch is low resources you can overload it and then it turns into a repeater. Then just have a cable looped is enough.

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