Free Practice Questions for Juniper JN0-352 Exam

Root bridge election is based on comparing each switch's full Bridge Identifier, which combines the bridge priority value with the switch's MAC address, with priority always evaluated first and MAC address serving strictly as a tiebreaker when two or more switches present identical priority values. In this scenario, the network has been left entirely at the default spanning-tree configuration, meaning every switch is operating at the standard IEEE and Junos default bridge priority of 32768; since all three switches share the exact same priority value, the comparison necessarily falls through to the MAC address tiebreak, where the switch with the numerically lowest MAC address wins the election. Comparing the three addresses shown — 00:1a:2b:3c:4d:01, 00:1a:2b:3c:4d:02, and 00:1a:2b:3c:4d:03 — Switch A's address is the lowest, since only the final octet differs and 01 is less than both 02 and 03, making Switch A the elected root bridge. RSTP uses the identical Bridge ID comparison mechanism as legacy STP for root election, so there is no special 'median MAC address' rule that applies uniquely under RSTP, making that distractor factually invalid regardless of protocol version. The election process also does not require any manual bridge priority configuration to complete; the default priority value is entirely sufficient on its own to allow a deterministic election to occur, since default priorities are still numerically comparable Bridge IDs. Reference topics: Junos Enterprise Switching – Spanning Tree Protocols, Default Priority and MAC Address Tiebreaking.

The L column in this output identifies which IS-IS levels are active on each interface, using the standard bitmask where 1 represents Level 1 only and 3 represents both Level 1 and Level 2 combined. Interface ge-0/0/2.0 shows an L value of 1 and its Level 2 DR field explicitly reads Disabled, meaning Level 2 has not been enabled on that circuit at all; consequently no Level 2 adjacency can ever form there, regardless of what the neighboring router advertises, which confirms that statement as correct. The lo0.0 loopback interface shows Passive under both the Level 1 DR and Level 2 DR columns. A passive IS-IS interface is deliberately excluded from adjacency formation — no IIH PDUs are sent or expected on it — but its associated prefix is still injected into the router's own LSP and flooded throughout the area, which is precisely why loopbacks are configured as passive: to guarantee the router ID/loopback prefix is reachable network-wide without wasting adjacency overhead on an interface with no real neighbor. This confirms that R3 advertises its loopback address, while ruling out the claim that the loopback is used to form an adjacency. Regarding designated routers, all circuits shown here report 'Point to Point' rather than an actual DR system ID, because DR election in IS-IS is a construct exclusive to broadcast (LAN) circuits; point-to-point circuits never elect a DR, so the first statement is false. Reference topics: Junos Enterprise Routing – IS-IS, Interface Levels and Passive Interfaces.

Nonstop active routing's defining architectural feature is that the backup Routing Engine runs a fully live, active instance of the routing protocol daemon (rpd) in parallel with the primary Routing Engine's rpd instance, continuously, from the moment NSR and its prerequisite GRES are established — not merely at the instant a switchover begins. As protocol adjacencies form, routes are learned, and the RIB is updated on the primary Routing Engine, that same protocol and RIB state is mirrored in real time to the backup Routing Engine's rpd process through an internal synchronization mechanism, so the backup's protocol state remains a live, up-to-date replica of the primary's at essentially every moment during normal operation. When a switchover occurs, the backup Routing Engine simply assumes the primary role with protocol adjacencies, routing tables, and forwarding state already fully populated and current, allowing it to continue operating without re-establishing neighbor relationships or re-learning the network topology, which is what makes the switchover genuinely nonstop and invisible to neighboring routers. This is fundamentally different from graceful restart, where the restarting router must rebuild its state by requesting help from cooperating neighbors after the fact. The Packet Forwarding Engine plays no role in synchronizing protocol-layer information such as LSAs or BGP updates; that is strictly an rpd-to-rpd function coordinated through the Routing Engine synchronization infrastructure. Reference topics: Junos Enterprise Routing – High Availability, Nonstop Active Routing Architecture and rpd Synchronization.

Junos firewall filters evaluate terms sequentially from top to bottom, and a term is only terminal for a packet if its then clause contains an explicit terminating action such as accept, discard, reject, or next term without a match. The count and log actions used in track-icmp are non-terminating; they update statistics and generate a log entry but do not stop evaluation, so a matching ICMP packet falls through to the next term after being counted. The second term, allow-tcp-established, matches only TCP packets carrying the ACK or RST flags as defined by the tcp-established keyword; an ICMP echo request does not satisfy protocol tcp, so this term is skipped entirely and does not accept the packet. Evaluation therefore reaches the implicit catch-all term block-rest, which has no from conditions and matches every remaining packet, incrementing blocked-counter and discarding it. The net effect for the described ICMP ping is that icmp-counter is incremented by the first term, the packet is neither accepted nor rejected by the second term, and blocked-counter is incremented immediately before the packet is silently discarded by the final term. This layered-term behavior, where counting is independent of the accept/discard decision, is a frequently tested nuance of Junos firewall filter processing logic. Reference topics: Junos Enterprise Switching – Layer 2 Security and Firewall Filters, Filter Term Evaluation Order.

The factory-default storm control configuration on EX Series switches operates in a purely rate-limiting mode rather than an interface-shutdown mode. When broadcast, multicast, or unknown-unicast traffic on a port exceeds the configured bandwidth-percentage threshold, the default action is simply to police the offending traffic type and silently drop only the packets that exceed that threshold, while all traffic within the allowed rate continues to be forwarded normally and the interface itself remains administratively and operationally up throughout the event. This explains the observed symptom precisely: during the burst of unknown-unicast frames, the switch dropped the excess volume above the configured limit, producing a brief period of packet loss, but as soon as the burst subsided and traffic fell back under the threshold, storm control simply stopped dropping packets and normal forwarding resumed automatically — no administrative shutdown, recovery timer, or manual intervention was ever involved, because the interface was never taken down in the first place. This default drop-only behavior is distinct from the optional interface-shutdown action, which must be explicitly configured if an administrator wants storm control to disable a port outright on violation (as seen in a related scenario requiring the clear ethernet-switching recovery-timeout command). Storm control by default covers broadcast, multicast, and unknown-unicast traffic types together, not multicast alone, and it has no functional relationship to GRES, which governs Routing Engine redundancy rather than Layer 2 traffic policing. Reference topics: Junos Enterprise Switching – Storm Control, Default Drop Behavior Versus Interface Shutdown Action.

Because Server A resides in VLAN 10 and Server B resides in VLAN 20, traffic between them cannot remain a purely Layer 2 switched flow; it must be routed between the two VLANs, which on Switch 1 means the packet traverses the switch's internal routing engine (via an IRB interface) between the ingress and egress switching stages. Junos processes firewall filters along this path in a strict, layered order that mirrors the packet's actual journey through the device. First, any filter applied at the physical ingress port level (Rx-Port) is evaluated as the frame first arrives on ge-0/0/10. Next, any filter applied to the ingress VLAN (Rx-VLAN, i.e., VLAN 10) is evaluated as the frame is classified into its source broadcast domain. Because the destination subnet requires routing, the packet is then handed to the routing engine, where any input/ingress routed filter (Rx-Router) applied to the receiving IRB interface is evaluated next, followed by any output/egress routed filter (Tx-Router) applied as the now-routed packet is handed from the routing engine back out toward VLAN 20. Finally, the packet passes through any egress VLAN filter (Tx-VLAN, for VLAN 20) and then the egress physical port filter (Tx-Port) on ge-0/0/20 immediately before transmission to Server B. This complete six-stage sequence — Rx-Port, Rx-VLAN, Rx-Router, Tx-Router, Tx-VLAN, Tx-Port — reflects every filter-evaluation checkpoint a routed, inter-VLAN packet passes through on an EX Series Layer 3 switch. Reference topics: Junos Enterprise Switching – Layer 2 Switching and Firewall Filter Processing Order for Routed VLAN Traffic.

The metric that OSPF assigns to a destination is visible from two complementary vantage points in Junos. The show route protocol ospf command displays the main routing table filtered to OSPF-learned prefixes, and each entry shows the computed cost alongside the next hop, exactly as it was installed after SPF calculation. The show ospf route command (which accepts filters such as intra-area, inter-area, and extern) presents the OSPF-specific routing table, organized by route type, and explicitly lists the metric column for every intra-area, inter-area, and external route the local router has calculated. Together these two commands give both the RIB-level and the protocol-level view of route cost. By contrast, show ospf database extensive dumps the raw link-state advertisements, where metrics appear only as link-level values buried inside Router or Network LSAs rather than as a resolved route cost, so it is not the direct tool for viewing a route's metric. show ospf interface reports interface operational state, area, and DR/BDR information but does not present a cost or metric field at all in its standard output. Candidates should be comfortable distinguishing the RIB-oriented and protocol-table-oriented verification commands, since JNCIS-ENT scenarios frequently test whether a candidate reaches for the correct show command layer during troubleshooting. Reference topics: Junos Enterprise Routing – OSPF Operation and Verification, Monitoring OSPF.

Configuring interface-type p2p under an OSPF interface tells Junos to treat that interface as a point-to-point network type regardless of the underlying physical medium, which removes the interface from the standard broadcast-network state machine entirely. On a true broadcast network, two routers must first complete a Designated Router and Backup Designated Router election, wait through the associated timers, and only then proceed through 2-Way, ExStart, Exchange, and Loading before reaching Full — a multi-step process. A point-to-point interface skips DR/BDR election altogether and proceeds directly from 2-Way into ExStart, so adjacencies form measurably faster, which is the first correct benefit. Because there is no DR on a point-to-point interface, Junos also does not generate a Type 2 Network LSA to describe the segment; the connected subnet is instead advertised as a simple stub-network entry inside the Router LSA itself, eliminating an entire LSA type from the area's link-state database and reducing its overall size, which is the second correct benefit. Point-to-point configuration is entirely incompatible with DR election, so a router configured this way cannot 'win' a DR election — there is no DR to win. Advertisement of the connected network happens on any operational OSPF interface irrespective of network type, so that option describes normal OSPF behavior rather than a benefit specific to the point-to-point setting. Reference topics: Junos Enterprise Routing – OSPF Network Types, Configuring OSPF Interface Type.

The show spanning-tree bridge command is specifically designed to surface exactly the two pieces of information required in this scenario within a single output. Its Root ID field reports the full Bridge Identifier (priority and MAC address) of whichever switch has been elected root bridge for the spanning-tree instance in question, immediately answering which switch in the campus network is currently acting as root, regardless of whether that happens to be the local device or a remote one. In the same output, the command's Root port field explicitly names the specific local interface (for example, ge-0/0/1.0) that the local switch has selected as its path toward that root bridge, directly answering the second part of the requirement without needing to cross-reference a separate command. Together, these two fields give a complete, immediate picture of both root bridge identity and local root port selection from one operational command. show spanning-tree interface instead presents a per-interface breakdown of STP role (root, designated, alternate, backup) and state across all local ports, which can indirectly reveal the root port by looking for the 'Root' role, but it does not directly report the Root ID/root bridge identity in the same structured way that show spanning-tree bridge does. show ethernet-switching table and show ethernet-switching interface pertain entirely to MAC address learning and switching-specific interface configuration respectively, and neither surfaces any spanning-tree topology or root bridge information at all. Reference topics: Junos Enterprise Switching – Spanning Tree Protocols, Verifying Root Bridge and Root Port with show spanning-tree bridge.