CCIE Routing & Switching Question of the Week: IS-IS

Answer: C.

IS-IS rides directly on the data link layer that it is configured for by using the Layer 2 addressing as the sub-network point of attachment (SNPA) to form neighbor relationships. As a link state protocol, like Open Shortest Path First (OSPF), IS-IS does not understand the concept of non-broadcast multiple-access (NBMA) networks. It sees networks as either point-to-point or as multi-access local area networks (LAN). IS-IS can have multiple transit areas and does not need virtual links.