Correct Answer: A,C,D
Explanation/Reference:
Explanation:
An IS (Intermediate system) is identified by an address known as a network access point (NASAP). The NSAP is divided up into three parts as specified by ISO/AI 10589:
Area address--This field is of variable length, composed of high order octets, and it excludes the System ID and N-selector (NSEL) fields. This area address is associated wit a single area within the routing domain.
System ID--This field is 6 octets long and should be set to a unique value with Level 1 and Level The system IS defines an end system (ES) or an IS in an area. You configure the area address and the system ID with the NET command. You can display the system ID with the show isis topology command.
NSEL--This field is called the N-selector, also referred to as the NSAP, and it specifies the upper- layer protocol. The NSEL is the last byte of the NSAP and identifies a network service user. A network service user is a transport entity or the IS network entity itself. When the N-selector is set to zero, the entire NSAP is called a network entity title (NET).
A NET is an NSAP where the last byte is always the n-selector and is always zero. A NET can be from 8 to
20 bytes in length.
Reference: http://www.cisco.com/c/en/us/td/docs/ios/iproute_isis/command/reference/irs_book/irs_is2.html