the Hearth :ms_agender_flag:
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what would happen if you plugged a network switch into itself
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Frost [moved]

@Felthry ...... feedback loop?

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Mattie :trans_furr_white:​

@Felthry you double the Internet speed

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mixed berry social anxiety disorder 🍓

@Felthry my guess would be that it just wouldn't do anything

either because the protocol is designed in such a way that it wouldn't cause a problem, or because the switch itself will notice and handle it

i can't imagine that that's a difficult problem in 2020, someone would have done something by now

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the Hearth :ms_agender_flag:

@monorail probably! but i'm curious what happens anyway
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mixed berry social anxiety disorder 🍓

@Felthry yeah I feel that "but what if I go out of my way to cause problems" impulse, like i want to see what would happen

one time in a networking class the teacher put his phone's MAC address on the whiteboard just to show us what a MAC address looks like, and explained that it's how the network keeps track of the devices connected to it

i asked him what would happen if two people had the same MAC address and he said "oh it wouldn't happen, this part of the address is a code that refers to a network chip manufacturer and the rest of it is that manufacturer's responsibility to keep unique"

"right, but what if i spoofed it"

".........i actually have no idea, want to try?"

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mixed berry social anxiety disorder 🍓

@Felthry it wasn't really exciting, it just knocked us both off the network, but it was fun

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Many Colors, Maybe Moved

@monorail @Felthry .c “knocked us both off the network” is definitely exciting to a certain category of people

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the Hearth :ms_agender_flag:

@monorail apparently @rey did the plug-a-switch-into-itself thing and it destroyed the switch, also
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mixed berry social anxiety disorder 🍓

@Felthry @rey o funk

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shork

@Felthry @monorail @rey it shouldn't break things unless it's like, power-over-Ethernet

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the Hearth :ms_agender_flag:

@noiob @monorail @rey PoE won't break things either, every ethernet jack has transformer isolation to 1000 V
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shork

@Felthry @monorail @rey ah, all I've heard is to be careful with it. I guess it corrupted its firmware or sth

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shork

@Felthry @monorail @rey that should also not happen, but unfortunately, computers

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shork

@Felthry usually the network goes down

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shork

@Felthry that actually happened at my workplace this year, someone plugged both ends of a network cable into a socket when cleaning up for the day and went home. I'm sure it was fun to debug

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Holly Bnuuy Lotor :verified:

networking tech 

@Felthry so i just tried it on my own switch, a 24 port unmanaged gigabit ethernet switch. once i did so, all of the activity lights for each port currently plugged in, including the two linked to themselves, started blinking a lot as if managing a lot of traffic from all of the ports. i unplugged the cable and this stopped.

i then decided to look it up instead of experimenting without looking information up first. turns out doing this on a basic switch can cause the switch to repeatedly send packets to itself, faster and faster, until it takes down the network. If the switch supports a more advanced feature known as the spanning tree protocol, though, it'll realize that it's plugged into itself and disable those ports.
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the Hearth :ms_agender_flag:

re: networking tech 

@holly I'm a little surprised there's no failsafe but I guess if it was able to enumerate what was downstream it would be a router, not a switch

i imagine any old router would figure out what's going on if plugged into itself
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Holly Bnuuy Lotor :verified:

re: networking tech 

@Felthry honestly, prior to the test and the research, i was running with the assumption that a basic, unmanaged switch wouldn't have done anything odd. i was thinking that it simply wouldn't have ever needed a reason to send any traffic between those two ports, since neither of them wouldn't have attempted to establish a connection. then, on the flipside, i assumed a managed switch might've had a hard time since it might end up doing some thinking on its own about what's plugged into it and the like, and the unexpected connection to itself might be a case it's not expecting.

turns out, no, it causes a lot of problems for an unmanaged switch since it does just enough on its own to get itself in trouble, and a managed switch's probably designed to recognize the upcoming problem and neutralize it. you learn something new each day, i guess, hahah.
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mixed berry social anxiety disorder 🍓

re: networking tech 

@holly @Felthry yeah, what i guessed would happen is that when the router says every once in a while "everyone please make yourself known" or whatever (i don't remember exactly how this works), the switch would say over one port "who are you"

and then it would receive "who are you" on the other port and say "i'm a switch"

and then when it got "i'm a switch" on the first port it would figure it out

i guess not

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Frost [moved]

networking tech 

@holly @Felthry So it IS (sometimes) a feedback loop, hah!

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