Ancestors

Written by Richard "mtfnpy" Harman on 2025-01-22 at 02:01

@tracketpacer hey, along the lines of "old ethernet tech" did you ever make a 10/100 ethernet vampire tap out of four keystone jacks and one length of cat5? I know they don't work with 1G ethernet (see @mossmann's throwing star LAN tap that had capacitors to knock the speed down to 100mbit)

One thing I always was curious about them was: why won't it !@#$ing work if you don't have the "monitor" interfaces connected?

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Toot

Written by Richard "mtfnpy" Harman on 2025-01-22 at 02:02

@tracketpacer

My wild guess today now knowing a tiny bit more about electricity is that the vampire tap basically created a stub that caused reflections that fucks up signal integrity, and when you actually connect the monitoring interfaces to another NIC, the monitoring NIC actually consumes the reflection.

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Descendants

Written by Michael Ossmann on 2025-01-22 at 02:16

@xabean @tracketpacer Yeah, it's the stub. They usually work fine without the monitor cable connected at all. The bad reflection happens when there is a monitor cable connected on only one end (connected to the tap but not the monitor host).

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Written by Richard "mtfnpy" Harman on 2025-01-22 at 02:19

@mossmann @tracketpacer thank you for the confirmation!

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