I just finished troubleshooting a network with an HP LaserJet 5si printer on the network that went offline. They were using an Ethernet to parallel port adapter to connect the printer. The first thing I did was run an arp -a and did not see the IP address for the printer. I then checked all the connections and cables and found nothing. Just before I decided to get a new Ethernet to parallel adapter I decided to ping the printer IP and to my surprise it pinged. I then ran another arp -a and it was now there and everything began to work. I am still suspect of the adapter but not sure why the ping seemed to fix the problem. I was hoping someone out there could shed some light on this for me.