IS-IS supports two fundamental circuit types: broadcast multiaccess and point-to-point. A broadcast or multiaccess circuit is used on media such as Ethernet where multiple routers can share the same Layer 2 segment. In that case, IS-IS elects a designated intermediate system to simplify database synchronization on the shared network. A point-to-point circuit is used where exactly two IS-IS routers form an adjacency across a direct link, which is common in modern routed campus, data center, and WAN designs. IS-IS does not use the same nonbroadcast multiaccess and point-to-multipoint network-type model that is familiar from OSPF.
When IS-IS must run across technologies that do not naturally behave like Ethernet broadcast media, the design is typically adapted with point-to-point subinterfaces or appropriate Layer 2 treatment rather than selecting an IS-IS NBMA circuit type. Therefore, from the listed choices, the supported IS-IS circuit types are multiaccess and point-to-point.