Jetdirect Drops Network Connections

Symptom: HP printer with embedded Jetdirect, won't print from lpr, lpd, etc., and the telnet admin is not available even though these features are enabled. When you telnet a.b.c.d, you connect and are immediately disconnected. When you telnet a.b.c.d 515, you also connect and disconnect, instead of getting the lpr/lpd protocol.

Cause: Direct from the page on web admin: "To reconnect to your printer after a reset, you must use the factory-default values."

Solution: Web interface ... Networking tab ... Security Settings page. Print the page to get the current settings, Click "Restore defaults", and then re-apply your settings.

Tested on a hp LaserJet 4350, should be similar on other models.