There is provided configuration of a secondary cellular network node for a secondary serving cell associated with a primary serving cell in a carrier aggregation enabled communications network. The secondary cellular network node receives an indication from a primary cellular network node associated with the primary serving cell to start scanning an unlicensed frequency band for deployment of the secondary serving cell. The secondary cellular network node scans at least one unlicensed frequency band to determine whether or not interference from transmitting interferers is present in the at least one unlicensed frequency band. The secondary cellular network node determines, based on the scanning, at least one frequency interval of the at least one unlicensed frequency band substantially free from the transmitting interferers. The secondary cellular network node transmits first configuration information of the at least one frequency interval to the primary cellular network node. The secondary cellular network node deploys the secondary serving cell by configuring the secondary cellular network node for transmission in one of the at least one frequency interval according to second configuration information being based on the first configuration information.