No additional ports are needed to open for PolyBase itself, except in the case of a PolyBase scale-out group. Without a scale-out group, the PolyBase service alone should not require any firewall rule.
On Windows servers, PolyBase will leverage the ports used by SQL Server in the IPAll section of the TCP/IP settings in SQL Server Configuration Manager. For more information, see TCP/IP Properties. On Linux servers, PolyBase will leverage the network.tcpport setting. For more information, see TCP port.
For PolyBase scale-out groups over multiple Windows servers, see port information in the next question.
However, you must allow other ports for communication to the various external data source(s) used by PolyBase. Refer to ODBC configuration, Azure resource configuration, or specific data source documentation. For example:
Source platformReference Microsoft SQL ServerPorts Used By SQL Server Hortonworks HDPAdministering HDFS Cloudera CDHPorts Used by CDH Components