Exam JN0-664 topic 1 question 33 discussion

Based on AJSPR course; Not A. because the local router moves its own local tuple into the tree database (and not into candidate database) Not C. because SPF algorithm moves the tuple with the lowest cost from the candidate database into the tree database. (and not into the LSB) Not D. because Step 1 (router determining cost from root to each neighbor ID) is repeated until the candidate database is empty. (and not until the tree database is empty) Therefore the answer is B. because if a new neighbor ID appears in the tree database, any tuples in the LSDB with a router ID equal to the new tree entry’s neighbor ID are moved into the candidate database.

A The correct statement about IS-IS when it performs the Dijkstra algorithm is: A. The local router moves its own local tuples into the candidate database. Explanation: When IS-IS performs the Dijkstra algorithm (Shortest Path First algorithm), the local router begins by moving its own local tuples (information about its directly connected neighbors and links) into the candidate database. These tuples represent the starting point for calculating the shortest paths to other nodes in the network. The other options are incorrect because: B is inaccurate: the candidate database stores tuples based on cost, not just matching router IDs. C is incorrect: tuples with the lowest cost are moved from the candidate database to the tree, not the LSDB. D is incorrect: the algorithm stops when the candidate database is empty, not the tree database.

In the context of the Dijkstra algorithm, the local router includes its own local information (like its own metrics and links) into the candidate database, which represents possible next hops and their associated costs for routing decisions. The other statements are not accurate in the context of how the Dijkstra algorithm operates in IS-IS: B. This statement is incorrect because the algorithm does not move neighbor IDs based on a match with router IDs in the LSD (Link State Database) directly into the candidate database. C. This is misleading; tuples with lowest cost are processed in the algorithm, but not necessarily "moved" to the LSDB (Link State Database) in this manner. D. The algorithm does not stop processing simply when the tree database is empty; it continues until it has found the shortest path to all reachable nodes.

B is correct

candidate database is not the same as tree database

There is a part on "Advanced Junos Service Provider Routing On-Demand " that says: "The candidate database is not empty, so the algorithm continues". Well, we can presume if the database is empty, algorithm stops.