DIS and DR Election
* The IS-IS Designated Intermediate System (DIS) is responsible for generating and updating pseudonode LSPs on a broadcast network.
* Unlike OSPF DR, the IS-IS DIS does not preempt by default. This behavior avoids unnecessary flapping in the network due to frequent DIS re-elections.
HCIP-Datacom-Core Reference
* The characteristics of DIS and DR behavior are explained in IS-IS network operation chapters.

In PIM-DM (Protocol Independent Multicast - Dense Mode), the SPT (Shortest Path Tree) establishment process involves flooding to propagate multicast traffic across the network, prune messages to stop sending multicast traffic to unwanted interfaces, and graft messages to re-establish forwarding when needed. State- refresh is not directly involved in SPT establishment but helps maintain the prune state .

Comprehensive and Detailed Step-by-Step Explanation:
* Portal Authentication:
* Portal authentication uses a web-based mechanism where clients are redirected to a login page.
* Communication between the access device and Portal server uses HTTP or HTTPS protocols.
* Correct Statements:
* Option A: HTTP or HTTPS is used for Portal authentication.
* Option D: Portal protocol packets are transmitted over TCP for reliable communication.
* Incorrect Statements:
* Option B: Port 2000 is not the default for processing Portal packets.
* Option C: The default destination port for communication with the Portal server is not 50100.
References:
* HCIA-Datacom Study Guide, Chapter: WLAN Portal Authentication
Huawei WLAN Authentication Protocols