HP Color LaserJet DHCP option 119 bug

A little while ago I was testing a Polycom CX700 phone for Microsoft Office Communications Server. This is a very clever phone that runs Windows CE and the Office Communicator Phone edition. The phone configures itself entirely from the network (DHCP and DNS). So in order for it work work correctly I was changing several DHCP settings.

Shortly after getting my new phone working I noticed that my HP Color LaserJet CP3505dn stopped working correctly. It would only appear to print one page, immediately after turning it on. I was finding myself having to turn it off and on repeatedly just to get a few pages out of it. Strangely the LCD menu seemed to also grind to a halt after about 30 seconds of being switched on, the buttons would take increasingly longer to respond until it stopped altogether.

I started to dig deeper and noticed that it would come back to life if I unplugged the network cable, but stopped responding 30 seconds or so after plugging it in again (it would also print out about 1 page if there was something in the queue on the print server). I then looked at its internal web page and I noticed the majority of the links and settings were missing:

I thought back to any changes I may have made recently and I remembered my DHCP settings. I went through and removed all the custom settings I had added for the Polycom CX700 (a.k.a. ‘Tanjay’) and to my surprise the printer fixed itself! Everything on the printer was working again correctly, including the web admin page, which had all its settings and links returned:

I narrowed the problem down to a DHCP option ‘119 – Domain Suffix Search’. If anything was set in this DHCP option, the printer would stop working.

So be warned network admins that have any HP LaserJet’s that get their IP address from DHCP! Setting option 119, might cause your printers to stop working.

The main reason I am sharing this is because I first tried to tell HP about this. I thought that since I had clearly discovered a bug in their firmware, they would want to know about it. After opening a support case with them, and receiving the usual ‘have you tried turning it off and on again’ reply, they went silent. I tried to follow it up, but every single one of my emails went unanswered. Since I usually Google for answers to problems like this – and not finding any this time – I thought I should share this, so someone else might find this solution and save themselves some time!

Ben Nichols
BN Information Security Limited