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

August 22, 2014 Johnny Bass Cisco, Cloudera, Featured, Professional Development, Project Management, Routing & Switching, Technology, Training in Business

Which statement is true about Intermediate System-to-Intermediate System (IS-IS)?

A. IS-IS provides direct support for NBMA networks.
B. IS-IS has a “virtual-link” concept similar to OSPF.
C. IS-IS packets are directly encapsulated in the data-link layer.
D. IS-IS is a hybrid between distance-vector protocol and link-state protocol.

Reveal Answer

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.

CCIE Routing & Switching Question of the Week Series

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

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