Here is how to factory reset an HP Jetdirect 170X external print server.

HP Jetdirect 170X External Print Server

1. Unplug the power to the Jetdirect.
2. Press and hold the “Test” button while plugging the power back in for 5 seconds.
3. The Jetdirect should be reset now and is configured by default to obtain an IP address automatically.

I have embedded the PDF manual for the Jetdirect 170x Installation and Configuration manual.

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00758101/c00758101.pdf