What documentation are you using to base YOUR answer on? Since you've researched your question and already come to an answer why did you ask?
According to this
webpage, the 20E, 40E and 80E are the only PLC5's that
natively support ethernet.
The 30 has 2 DH+/RIO and standard RS-232.
However, you can install a
1785-ENET in the rack to provide ethernet comm to a PLC5.
But to answer your question, the PLC5/30 does NOT have built-in support for ethernet com.