Ethernet Monitor

[Dave Liquorice]

Is there a cheap box that will show, via some LEDs, if there is traffic flowing in an ethernet cable (up to gigabit, all four pairs). Doesn't need to know anything about the data just that data is flowing. It must not interfere with the data or upset the connection, so I don't think a T connection and a cheap switch will work and I'd rather it was line powered.

I have a sneaky feeling that a simple buffer driving an LED for each pair won't work as the volts waggle all the time due to the DC compensation and NRZI coding.

[Andy Burns]

You seem to have ruled out the simplest way of doing it, just use two ports of a switch, no need for any "T" just use two ports and an extra cable.

[The Natural Philosopher]

[Graham.]

I assume you are monitoring for unauthorised use. What about the ARP traffic and other housekeeping stuff that occurs when two NICs are connected?

[The Natural Philosopher]

Its pretty low

[Dave Liquorice]

No just want to see if the link is working. Something that can sit in circuit and not consume any external power. Having engaged brain a bit more the lights on any connected kit would do but there might not be any connected kit and connecting kit, if there is any available, might not be convenient. So it boils down to a line powered "is there a live switch on the other end of this cable?"

That ain't going to work as there is no DC coming out of a live switches port. I guess their might be the "carrier" of a few tens of MHz but detecting that is starting to get complicated. Think it's time to go back to sleep and just have a spare switch kicking about. B-)