RSTP is abbreviation of Rapid Spanning Tree Protocol and supported in Easergy P3 when the double port Ethernet communication board is available. For details of RSTP, please download the application note P3_EN_AN_A002. WEB link:
https://www.se.com/ww/en/download/document/P3_EN_AN_xxxx/
https://www.se.com/ww/en/download/document/P3_EN_AN_xxxx/