JN0-364 Certification Exam Guide + Practice Questions Updated 2026

Explanation:
When designing High Availability (HA) for Juniper Service Provider routers, understanding the interaction between the control plane and data plane is vital. The user has already enabled Graceful Routing Engine Switchover (GRES), which synchronizes the interface and kernel state between the primary and backup Routing Engines (REs). However, GRES by itself does not preserve the routing protocol state (like OSPF adjacencies or BGP sessions).
To achieve the preservation of the routing protocol state without relying on external "helper" routers, you must implement Non-Stop Active Routing (NSR). According to Juniper Networks documentation, NSR uses the infrastructure provided by GRES to also synchronize the routing protocol process (rpd) information. Under NSR, the backup RE maintains a "hot" standby state of all routing protocols. If the primary RE fails, the backup RE takes over immediately. Because it already possesses the full routing table and peer session states, the peering neighbors are unaware that a switchover occurred. No protocol adjacency resets occur, and traffic continues to flow uninterrupted.
It is crucial to differentiate NSR from Graceful Restart (Option C). While Graceful Restart also aims to maintain traffic flow during a switchover, it does require help from neighboring routers (known as "helper mode"). If the neighbors do not support or are not configured for Graceful Restart, the sessions will drop. Since the user explicitly stated they want to "avoid relying on helper routers, " Graceful Restart is not the correct solution.
Non-stop Active Bridging (Option A) provides a similar "hitless" failover but specifically for Layer 2 environments (STP/VLANs) rather than Layer 3 routing protocols. BFD (Option B) is a failure detection protocol used to speed up convergence but does not preserve state during an RE failover; in fact, without NSR, BFD would likely trigger a faster teardown of the session during a switchover. Therefore, NSR is the only feature that meets the requirement for independent control-plane preservation.

Explanation:
In the Junos OS architecture, route preference (often referred to as administrative distance in other vendor platforms) is the primary metric used by the Routing Engine to select the "best" path when multiple protocols provide a route to the same destination. Each routing protocol and route type is assigned a default numeric value; the lower the value, the more preferred the route.
According to Juniper Networks technical documentation, an aggregate route is assigned a default preference of 130. Aggregate routes are a form of static-like route used to group specific routes into a single, broader prefix to reduce the size of routing tables and limit the scope of routing updates. They are "protocol-independent" because they are not learned from a dynamic neighbor but are manually defined by the administrator.
To understand where130fits in the hierarchy, it is helpful to compare it with other common Junos preferences:
Directly connected interfaces: 0
Static routes: 5
OSPF Internal: 10
IS-IS Level 1/2: 15/18
Aggregate routes: 130
OSPF AS External: 150
BGP (Internal and External): 170
Generated routes: 150
By setting the aggregate route preference to 130, Junos ensures that specific routes learned via IGPs (like OSPF or IS-IS) are preferred over the aggregate. This is essential because an aggregate route is often used as a "catch-all" or a discard route when more specific path information is missing. If the aggregate had a lower preference (like 5), it might override dynamic routing information, leading to suboptimal routing or black-holed traffic.

Explanation:
In the Juniper Networks Junos operating system, the management of routing information is partitioned into several distinct routing tables (RIBs), each serving a specific architectural purpose. When dealing with Multiprotocol Label Switching (MPLS), understanding the distinction between inet.0 and inet.3 is fundamental for troubleshooting and traffic engineering.
Theinet.3routing table is specifically designed to store the egress IPv4 addresses of Label-Switched Paths (LSPs). When an ingress router successfully establishes an LSP (via RSVP or LDP), it places the host address of the egress router (the tail-end) into the inet.3 table. This table is not used for general packet forwarding; instead, it is primarily used by the Border Gateway Protocol (BGP) for next-hop resolution. When BGP receives a route, it checks both inet.0 and inet.3 to resolve the next hop. If a matching entry exists in inet.3, the router knows it can reach that destination via an MPLS tunnel, allowing for the encapsulation of BGP traffic within MPLS.
In contrast, inet.0is the default unicast routing table used for standard IPv4 forwarding and contains routes learned via IGPs (OSPF, IS-IS) or static routing.inet.1is utilized for multicast forwarding (MBGP), andinet.2 is typically used for Multicast Source Discovery Protocol (MSDP) or RPF checks in multicast environments. By isolating LSP egress points in inet.3, Junos prevents MPLS-specific paths from interfering with standard IGP path selection unless the administrator explicitly chooses to merge them (e.g., using the traffic-engineering bgp-igp command). Therefore, by default, the ingress router maintains its list of reachable LSP endpoints in inet.3.

Explanation:
In a Juniper Networks environment, when a router receives multiple BGP paths for the same destination prefix, it utilizes the BGP Path Selection Algorithm to determine the single "best" path to install in the routing table and advertise to other peers. This selection process follows a strict hierarchy of attributes.
According to Juniper Networks technical documentation, the very first attribute evaluated by the BGP process (after ensuring the next hop is reachable) is the Local Preference. Local preference is a well-known discretionary attribute used to communicate a preference for a specific exit point from the local Autonomous System (AS). A higher local preference value is always preferred over a lower one.
Analyzing the exhibit:
R3receives the prefix from R1 and applies an export policy to its IBGP session that sets the local preference to 150.
R4receives the same prefix from R2 and applies an export policy to its IBGP session that sets the local preference to 200.
R5receives both of these IBGP updates from R3 and R4.
When R5 runs the best-path algorithm for the 203.0.113.0/24 prefix, it compares the local preference values. Since the path from R4 has a local preference of 200 and the path from R3 has a local preference of 150, R5 immediately selects the path fromR4as the best route. Because BGP is designed to prevent loops and maintain a consistent view, only this single best path is installed as the active route in R5's routing table (inet.0). Options B and D are incorrect because they imply multiple paths are installed for forwarding, which only occurs if specific multipath load-balancing is configured, which is not indicated here.