N26 interface is an inter-Core Network interface between the MME and 5GS AMF in order to enable interworking between EPC and the NG core.
Inter-RAT Mobility procedures involving mobility between LTE-EPC and 5G-NR-5GS utilize the N26 interface which enables the exchange of Mobility Management(MM) and Session Management (SM) states between the source and target RAT network.
N26 support provides IP address continuity on inter-system mobility to UEs that support 5GC NAS and EPC NAS
Continue reading: What is N26 Interface in 5G and what's its importance? - wirelessbrew.com