HP Jetdirect 250M User Manual page 49

Check the lights. When you plug the print server into the printer, the
status light should start blinking green as it executes the self-test. After
the print server completes the self-test, the light should continue to
blink green as long as the network cable is not plugged in. When you
plug in the network cable, the status light should change to solid green
to indicate a valid network connection. In addition, one of the two link
lights (the "10" light or the "100" light) should come on solid green, to
indicate the speed of the network connection (10 or 100 megabits per
second).
If the status and link lights fail to exhibit this behavior (different color or
different blink pattern), there is a problem. Click here for the