If the UE indicates support for N1 mode in the ATTACH REQUEST message and the MME supports inter-system interworking with 5GS, the MME may set the IWK N26 bit to either: - "interworking without N26 not supported" if the MME does not support interworking procedures without N26 interface; or - "interworking without N26 supported" if the MME supports interworking procedures without N26 interface in the EPS network feature support IE in the ATTACH ACCEPT message.