JN0-364 Exam Preparation Material | Service Provider Routing and Switching - Specialist (JNCIS-SP)

Explanation:
The transition to IPv6 requires routing protocols that are capable of carrying 128-bit address information.
Juniper Networks Junos OS supports several "IPv6-ready" protocols for dynamic routing.

Explanation:
In the IS-IS (Intermediate System to Intermediate System) protocol, the process of forming an adjacency between two neighbors follows a specific sequence of states. While OSPF uses states like "Init, " "Two-Way, " and "Full, " IS-IS uses a slightly different nomenclature within its state machine.
According to Juniper Networks technical documentation, when a router first sends an IS-IS Hello (IIH) PDU and receives one back from a neighbor, but has not yet confirmed that the neighbor "sees" it back, the adjacency enters the Initializing state. Specifically, on a point-to-point link, the state transitions from Down to Initializing as soon as the first PDU is received. On a broadcast network (like Ethernet), the Initializing state indicates that the local router has received a Hello PDU from the neighbor, but the local router's own System ID is not yet listed in the neighbor's list of "seen" neighbors (the neighbor's Hello PDU does not yet contain the local router's MAC address).
The adjacency only moves to the Upstate (Option C) once bi-directional communication is confirmed― meaning both routers have seen each other's System IDs in the incoming Hello PDUs.
Why other options are incorrect:
Loading (Option A): This is an OSPF state, not an IS-IS state. In IS-IS, database synchronization happens after the adjacency is Up.
Two-Way (Option D): While functionally similar to the state IS-IS is achieving, "Two-Way" is the specific terminology for OSPF. In IS-IS, the intermediate step between knowing a neighbor exists and having a fully functional adjacency is strictly called Initializing.

Explanation:
In Junos OS, the Routing Engine maintains several different tables to manage various types of reachability and forwarding information. When a router is running MPLS, it must track both IP routes and label-to-label mappings.
Thempls.0table is the primary repository for the Label Information Base (LIB) and the Label Forwarding Information Base (LFIB). According to Juniper Networks documentation, mpls.0 is used by transit and egress routers to perform label lookups. When a labeled packet arrives at an interface, the router looks at the top label and references the mpls.0 table to determine the next action. This table stores the mapping of incoming labels to their corresponding operations: Pop (remove the label), Swap (replace the label), or Push (add an additional label).
It is crucial to understand the roles of the other tables to avoid confusion:
inet.0 (Option D): This is the default unicast routing table for IPv4, used for standard IP-to-IP forwarding.
inet.3 (Option C): This is the MPLS Path Table. It stores the egress loopback addresses of LSPs and is used by BGP for next-hop resolution to determine if a destination can be reached via an MPLS tunnel. While inet.3 knows about LSPs, the actual label-switching instructions reside in mpls.0.
inet6.0 (Option A): This is the default unicast routing table for IPv6.
Therefore, for the specific purpose of storing the label base used for transit switching operations, mpls.0is the correct and only table used in the Junos architecture.

Explanation:
In Junos OS, understanding the distinction between the Routing Information Base (RIB) and the Forwarding Information Base (FIB) is fundamental to analyzing traffic patterns and load-balancing behavior. The RIB (show route) contains all prefixes learned via various protocols, while the FIB (show route forwarding-table) contains only the active next-hops that are actually programmed into the Packet Forwarding Engine (PFE).
According to Juniper Networks technical documentation, the default behavior for Junos OS when encountering Equal-Cost Multipath (ECMP) routes is to select only a single next-hop from the available candidates in the RIB and install that single path into the FIB. In a default state, even if the show route output displays multiple next-hops for a destination like 172.24.0.0/24, only one would have the active route symbol ( >) and only that one would appear in the forwarding table.
In the provided exhibit, the show route output shows two next-hops for 172.24.0.0/24, but only the first one (172.20.0.2) is marked with the>symbol as the active selection. However, the subsequent show route forwarding-table output reveals that both next-hops (172.20.0.2 and 172.20.1.2) are currently present in the forwarding table for that same destination. This discrepancy indicates that the default load-balancing behavior has been modified (Option B). This modification is typically achieved by creating a routing policy with the action then load-balance per-packet (which actually results in flow-based load balancing) and applying it to the forwarding table via the export statement under [edit routing-options forwarding-table].
Because the forwarding table now contains both next-hops, the router is no longer restricted to a single path. Therefore, the router will choose both next-hops in the routing table (Option D) for packet forwarding, distributing flows across the two available Gigabit Ethernet interfaces (ge-0/0/2.0 and ge-0/0/3.0). This ensures higher utilized bandwidth and provides redundancy at the data plane level.

Explanation:
In the Junos OS, routing policy behavior is governed by default import and export rules that vary significantly between different protocols. For IS-IS (Intermediate System to Intermediate System), the default export policy is "reject all." This means that, by default, an IS-IS process will export nothing from the routing table into the IS-IS database.
According to Juniper Networks technical documentation, IS-IS automatically advertises its own direct interfaces that are configured under the [edit protocols isis] hierarchy. However, it does not automatically redistribute routes learned from other sources―such as Static routes, OSPF, or BGP―into the IS-IS domain. This is a safety mechanism designed to prevent accidental routing loops or the flooding of unnecessary prefixes into the link-state database (LSDB), which could impact the stability of the SPF (Shortest Path First) algorithm.
To move routes from the routing table (inet.0) into IS-IS, an administrator must explicitly create a routing policy and apply it as an export policy within the IS-IS configuration.
For example:
Code snippet
set policy-options policy-statement REDIST-STATIC term 1 from protocol static
set policy-options policy-statement REDIST-STATIC term 1 then accept
set protocols isis export REDIST-STATIC
Without such a policy, the IS-IS LSPs (Link-State PDUs) will only contain information about the IS-IS enabled interfaces and the reachability of other IS-IS neighbors. This behavior contrasts with protocols like BGP, which has different default rules for exporting active BGP routes to EBGP peers. In the context of IS-IS in a Juniper environment, "export nothing" is the standard operational baseline.