Making a "mirror switch"

[new299]

Hi guys,

Recently I've been hacking around with cheap Chinese dumb switches. I picked up a bunch of eBay which were based on the IP178G. This is a cheap Chinese switch on a chip which as a (for Shenzhen) pretty good datasheet. I figured some people here might also be interested in the project.

Turns out there's a bunch of stuff you can configure on them using either a proprietary serial protocol, or from EEPROM on boot.

The whole EEPROM thing was a massive rabbit hole. The datasheet lists a AT24C01 to C16 EEPROM. That's a deprecated part. I figured the AT24C01A would be compatible. Turns out that's very much not the case:

http://41j.com/blog/2016/09/the-at24c01-and-the-at24c01a/

The AT24C01A added device addressing. The device address is set by 3 pins on the chip, and is also sent in every read/write op. The AT24C01 seems to be totally unavailable outside China. On taobao there appear to be a bunch of clones, and I guess it's alive and well in the Shenzhen supply chain.

So this meant I had to fallback to a microcontroller. I needed up using an ATTINY85 and document my initial experiments with an Arduino here:

http://41j.com/blog/2016/08/fiddling-with-a-cheap-5-port-dumb-switch-to-add-vlansport-mirroring/

and final version using an ATTINY85 here:

http://41j.com/blog/2016/09/mirrorswitch/

I've always wanted a switch with a static port mirroring configuration. This allows you to monitor traffic on a port, much like you used to be able to using hubs many years ago. I'm now selling them on my shop (basically a hobby, I've only sold one):

http://www.whitefordresearch.com/products/mirror-switch