Juniper Updated JN0-664 Exam Questions and Answers by angelo

Type 1: When Type value is 1, the Administrator field is 4-bytes and Assigned Number field is 2-bytes. The Administrator field should be set to the IP address (public IP addresses should be used). The Assigned Number field contains a number from a numbering space that is administered by the enterprise to which the IP address has been assigned by the appropriate authority.

the default behavior for iBGP is to propagate EBGP-learned prefixes without changing the next-hop. This can cause issues if the next-hop is not reachable via the IGP. One solution is to use the next-hop self command on R4, which will change the next-hop attribute to its own loopback address. This way, R5 can reach the next-hop via the IGP and install the route in its routing table.

Another solution is to add the external interface prefix (120.0.4.16/30) to the IGP routing tables of R4 and R5. This will also make the next-hop reachable via the IGP and allow R5 to use the route. According to 2, this is a possible workaround for a pure IP network, but it may not work well for an MPLS network.

The reason why the route is being hidden is that R5 cannot reach the BGP next hop 10.0.0.1, which is the address of R1. R5 does not have a route to 10.0.0.0/24 in its routing table, and neither does R4. Therefore, R5 cannot resolve the BGP next hop and marks the route as hidden.

There are two solutions that will solve this problem:

• Option A: On R4, create a policy to change the BGP next hop to itself and apply it to IBGP as an export policy. This way, R5 will receive the route with a next hop of 172.16.1.2, which is reachable via the IGP. This solution is also known as next-hop-self1.
• Option B: Add the external interface prefix to the IGP routing tables. This way, R4 and R5 will learn a route to 10.0.0.0/24 via the IGP and be able to resolve the BGP next hop. This solution is also known as recursive lookup2.

Option C is not correct because adding the internal interface prefix to the BGP routing tables will not help R5 reach the BGP next hop 10.0.0.1.

Option D is not correct because changing the BGP next hop to 172.16.1.1 on R4 will not help R5 either, since R5 does not have a route to 172.16.1.1 in its routing table.

References: 1: Configuring Next-Hop-Self for IBGP Peers 2: Understanding Recursive Lookup

IS-IS is a link-state routing protocol that uses the Dijkstra algorithm to compute the shortest paths between nodes in a network. The Dijkstra algorithm maintains three data structures: a tree database, a candidate database, and a link-state database (LSDB). The tree database contains the nodes that have been visited and their shortest distances from the source node. The candidate database contains the nodes that have not been visited yet and their tentative distances from the source node. The LSDB contains the topology information of the network, such as the links and their costs.

The Dijkstra algorithm works as follows:

• The local router moves its own local tuples into the tree database. A tuple consists of a node ID, a distance, and a parent node ID. The local router’s tuple has a distance of zero and no parent node.
• The local router moves its neighbors’ tuples into the candidate database. The neighbors’ tuples have distances equal to the costs of the links to them and parent node IDs equal to the local router’s node ID.
• The local router selects the tuple with the lowest distance from the candidate database and moves it to the tree database. This tuple becomes the current node.
• The local router updates the distances of the current node’s neighbors in the candidate database by adding the current node’s distance to the link costs. If a shorter distance is found, the parent node ID is also updated.
• The algorithm repeats steps 3 and 4 until either the destination node is reached or the candidate database is empty.