These days Hewlett Packard only sells two different internal print server cards for their printers, the HP Jetdirect 620n and the 635n:
http://h10010.www1.hp.com/wwpc/us/en/sm/WF04a/18972-18972-236253-34213-236264.html
The Jetdirect 635n allegedly has IPv6 support, and is therefore a suitable candidate to upgrade our HP Laserjet 4250, which' embedded