The　current　mobile　communications　could　not　satisfy　the　explosive　data　requirement　of　users.　This　paper　reviews　the　frontier　technology　of　software　definition　networks　(SDN)　of　5G　and　6G,　including　system　architecture,　resource　management,　mobility　management,　interference　management,　challenges,　and　open　issues.　First　of　all,　the　system　architectures　of　5G　and　6G　mobile　networks　are　introduced　based　on　SDN　technologies.　Then　typical　SDN-5G/6G　application　scenarios　and　key　issues　are　discussed.　We　also　focus　on　mobility　management　approaches　in　mobile　networks.　Besides,　three　types　of　mobility　management　mechanism　in　software　defined　5G/6G　are　described　and　compared.　We　then　summarize　the　current　interference　management　techniques　in　wireless　cellular　networks.　Next,　we　provide　a　brief　survey　of　interference　management　method　in　SDN-5G/6G.　Additionally,　considering　the　challenges,　we　discuss　mm-Wave　spectrum,　un-availability　of　popular　channel　model,　massive　MIMO,　low　latency　and　QoE,　energy　efficiency,　scalability,　mobility　and　routing,　inter　operability,　standardization　and　security　for　software　defined　5G/6G　networks.