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Comprehensive and Detailed In-Depth Explanation:

NET (Network Entity Title) is a special form of NSAP (Network Service Access Point) used in IS-IS routing.

NET consists of three fields:

AFI (Authority and Format Identifier) + IDI (Initial Domain Identifier) + Area Address → Identifies the area.

System ID → Uniquely identifies a router within an area (similar to an OSPF Router ID).

SEL (NSEL - N-selector) → Always 0 in a NET, as IS-IS operates at Layer 3.

Since System ID uniquely identifies a host/router within an area, the correct answer is A.

???? Reference: Huawei HCIA-Datacom Study Guide, IS-IS Addressing and NET Structure.

A is false – The default value of Local_Pref is 100, not 0.

B is false – Local_Pref is not advertised to EBGP peers, it is only sent to IBGP peers.

C is correct – The Local_Pref value stays constant unless modified by a route-policy or filter.

D is correct – Higher Local_Pref values indicate preferred paths, so BGP prefers the path with the highest Local_Pref among multiple options.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“Local_Pref is used to select the best outbound path for traffic leaving the AS. It is only shared among IBGP peers and defaults to 100. The higher the value, the more preferred the route.”

(Chapter: BGP Path Attributes – Section: Local Preference)