Resetting the Lexmark E323N network configuration

By Abhijit Menon-Sen <ams@toroid.org>

2010-09-12

Many years ago, I bought a Lexmark E323N laser printer (600dpi, 19ppm) because it was the cheapest printer I could find that came with Ethernet and PostScript support. I used it for a long time and was happy with it. When I moved away from home, I left it connected to my switch—along with a DSL modem and a wireless access point—so that my mother could use it.

Fast forward a few years. The DSL modem had died and been replaced. The switch had died and been replaced. The WAP died, and the Netgear WGR614 bought to replace it had four Ethernet ports, and could thus replace the switch as well. But it was a router, not a bridge, and so it wanted its internal and external networks numbered differently. The upshot was that the printer's IP address needed to change from 10.0.0.4 to 192.168.1.4.

No problem. I added a 10.0.0.0/8 address and host route to my netbook's eth2, which let me connect to the printer's administrative interface and change its address in the network settings menu. Alas, I forgot all about the separate "access control" menu, which was set to deny requests from outside 10.0.0.0/8. When the printer came back up, it would respond to ping from 192.168.1.x but discard TCP packets because of the access filter. If I used a 10.0.0.x address, it threw away all packets because they were from a source that did not match the printer's own IP address.

(I can't decide which is more stupid: that I chose to enable an IP-based packet filter on the printer in the first place, or that the printer did not protest at a configuration that rendered it unusable. I have a sinking feeling that it was the former.)

No problem. I went to the Lexmark web site and downloaded a user manual. I followed its description of the occult ritual to reset the printer's configuration settings, which involved opening the printer, switching it on, hopping in a clockwise half-circle on one leg, holding some buttons, staring at blinkenlights, and so on. I did it once, then twice. Nothing changed. Then I found this web page, which explained that the "reset to factory defaults" procedure didn't actually reset the network settings. I tried the NVRAM tweaking procedure described on that page (which involved pressing the continue and cancel buttons a gazillion times while watching blinking LED patterns for feedback), and it didn't seem to work either.

Despair set in. I tried the configuration tweaks again. So did Hassath. Nothing changed. My mother was muttering in the background about buying a new printer. After two or three more attempts, Hassath also gave up, and they both went downstairs to make coffee. I sat down to repeat the process. With tcpdump running, I went through the sequence once, twice, then ten times, then fifteen, then I lost count. Suddenly, just as the page said might happen, the printer emitted "several BOOTP packets and a burst of ARP probe packets". The Netgear answered its DHCP request, and just like that, the network settings were reset and everything worked again.

I can only guess that changing the network settings so many times so quickly triggered some bug in the firmware; perhaps the settings were saved incorrectly, leading to a checksum error when they were loaded, and thus forcing the printer to discard the saved settings. (I used a similar trick to fix my WAP54G.)

Remember: You need to continue tweaking the printer until a sensible IP address appears.