Pass the Juniper JNCIS-ENT JN0-352 Questions and answers with CertsForce

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.

Local preference is a well-known, discretionary BGP path attribute carried exclusively in IBGP UPDATE messages, and Junos assigns every route a local preference value of 100 by default whenever a route is received without an explicit LOCAL_PREF value already attached, or when the attribute has not been otherwise modified through routing policy. This default of 100 becomes the implicit baseline against which any administrator-configured local preference adjustments are compared. Because higher local preference values are always preferred over lower ones during BGP best-path selection — and this evaluation happens before AS path length, origin, or MED are ever considered — network engineers commonly use local preference specifically to steer outbound traffic leaving the autonomous system toward a preferred exit peer or upstream provider, by assigning a higher local preference to routes learned from that preferred peer relative to routes learned from alternative peers, making the third statement correct as well. Local preference is explicitly excluded from advertisement to EBGP peers under the BGP specification; it is meaningful only within the boundaries of a single AS and is stripped before a route crosses an AS boundary outward, since a neighboring AS has no reason to trust or honor another organization's internal preference values. A local preference of 0 does not have any special 'drop' semantics in BGP — it is simply the lowest possible numeric preference value and is treated like any other value during comparison, not as a discard instruction. Reference topics: Junos Enterprise Routing – BGP, Local Preference Defaults and Outbound Traffic Engineering.

The diagnostic output explicitly states the root cause: the local router has only the inet6-unicast address family configured for this peer, while the remote router advertised inet-unicast and inet-vpn-unicast in its OPEN message, and BGP requires at least one common negotiated address family (NLRI type) between two peers for a session to remain established; with zero overlap between the two sides' configured families, the session is torn down immediately after the OPEN exchange, which is precisely why the peer state shows Active rather than Established. This confirms the mismatched-address-family statement directly and unambiguously from the exhibit's own Down reason and Detail reason fields. The diagnostic tool's own embedded Suggestion text goes further, explicitly advising the administrator to additionally verify that the local-address configured for the peer matches the remote router's configured neighbor address and vice versa — a secondary, commonly encountered condition in which mismatched or effectively duplicated/incorrect address bindings between the two sides' neighbor statements can independently prevent a session from completing correctly, even once the family mismatch is resolved. This is why address-configuration consistency between the peers is flagged as a second concern worth checking in this scenario. Nothing in the exhibit references NTP or time synchronization at all, nor does anything in the output reference authentication, an MD5 mismatch, or any related failure signature; both of those conditions would present through entirely different diagnostic messages than the one shown here. Reference topics: Junos Enterprise Routing – BGP, Address Family Negotiation and the show bgp diagnostics neighbor Command.

Each of the 24 end-device-facing interfaces in this scenario needs to carry traffic for exactly one VLAN, and the end devices themselves are ordinary hosts that neither expect nor generate 802.1Q-tagged frames. This is precisely the definition of an access port in Junos: family ethernet-switching interface-mode is set to access, and a single vlan members statement assigns the port to VLAN 70. Access mode ensures frames egressing toward the host are untagged and any frames received are implicitly treated as belonging to the configured VLAN, which is both simpler to manage and more efficient than trunking, since access ports do not carry the 802.1Q tag overhead nor process VLAN pruning logic relevant only to multi-VLAN links. Trunk mode, by contrast, is reserved for switch-to-switch or switch-to-router links that must simultaneously carry frames for multiple VLANs, such as the uplink toward the distribution switch that transports VLANs 30, 50, and 70 together — configuring the 24 host-facing ports as trunks (with or without a native VLAN) would be functionally incorrect and operationally wasteful, since end devices have no need to interpret VLAN tags. There is also no such behavior in Junos where VLAN-ID numeric value dictates default port behavior, making the 'no configuration needed' option a distractor with no basis in EX Series switching architecture. Reference topics: Junos Enterprise Switching – VLANs, Configuring Access and Trunk Port Modes.

This detailed adjacency output shows R3 maintaining four separate, fully Up adjacencies, evenly split between the two IS-IS levels. R1 and R2 are both formed at Level 1, confirming that R3 is directly adjacent to exactly two Level 1 neighbors within its local area, which validates that statement. R4 and R5 are both formed at Level 2, and Level 2 adjacencies are, by definition, part of the IS-IS backbone that interconnects areas; a router maintaining any Level 2 adjacency is by that fact participating in and connected to the Level 2 backbone, confirming R3's backbone connectivity as well. Every one of the four listed adjacencies explicitly shows 'Speaks: IP, IPv6' in its detail output, which is Junos's way of indicating that both the IPv4 and IPv6 address families have been successfully negotiated and are active over that circuit; this directly contradicts, rather than supports, the claim that IPv6 is disabled on these neighbors — if IPv6 were disabled, the Speaks field would list only IP. Regarding authentication, the output contains no field, flag, or indication whatsoever referencing authentication configuration or state for the R5 adjacency (or any adjacency); Junos would typically surface authentication-related information separately if it were configured and relevant, and its complete absence here means no basis exists in the exhibit to conclude authentication is required for that specific adjacency. Reference topics: Junos Enterprise Routing – IS-IS, Level 1 and Level 2 Adjacencies and Address Family Negotiation.

In the output of show ospf database, Junos marks every self-originated link-state advertisement with an asterisk immediately preceding the LSA's link-state ID. A self-originated LSA is one that was created and flooded by the router on which the command is being executed, as opposed to an LSA that was received from and originated by a neighboring router elsewhere in the area. In this exhibit, the asterisked Router LSA has an ID of 10.101.100.0 and an Advertising Router value of the same 10.101.100.0, confirming that this particular Router LSA describes the local device's own links, area membership, and interface costs, and that the local router itself flooded this LSA into the area's link-state database. This distinction matters operationally because when troubleshooting OSPF topology or SPF calculation issues, engineers frequently need to isolate their own router's advertised state from the states advertised by every other router in the area; the asterisk provides an immediate, unambiguous visual cue for that separation without needing to cross-reference the router's own ID separately. It has no relationship to designated router or backup designated router status — DR/BDR roles are indicated elsewhere in interface-level output, not through the asterisk convention in the LSA database dump, and a router that is neither DR nor BDR still self-originates and flags its own Router LSA the same way. Reference topics: Junos Enterprise Routing – OSPF, Interpreting the OSPF Link-State Database.

Correctly blocking SSH traffic originating from a specific network requires matching three precise conditions simultaneously in the from clause: the traffic's source-address must equal the 192.168.10.0/24 network, since the requirement is to block traffic coming from that network rather than traffic destined to it; the protocol must be explicitly set to tcp, since SSH operates exclusively over TCP; and the destination-port must be set to 22, because an inbound SSH connection request is always directed at the well-known SSH listening port 22 on the receiving side, regardless of which ephemeral source port the initiating client happens to use. The first option satisfies all three conditions correctly and pairs them with a discard action, cleanly dropping matching traffic. The second option incorrectly substitutes destination-address for source-address, which would match traffic heading toward that /24 rather than traffic originating from it, inverting the intended match direction. The third option incorrectly uses source-port 22 instead of destination-port 22; since the SSH client's source port is a randomly assigned ephemeral value rather than a fixed 22, this term would almost never match real SSH session-initiation traffic. The fourth option relies on a service ssh match condition, which is not valid syntax within the standard Junos firewall filter grammar for family inet; there is no such application-based keyword available at that hierarchy, making the term invalid regardless of the reject action chosen. Reference topics: Junos Enterprise Switching – Firewall Filters, Matching on Address, Protocol, and Port Conditions.

Root bridge election in Spanning Tree Protocol is governed entirely by the Bridge Identifier, an 8-byte value formed by concatenating the configured bridge priority (the higher-order, more significant portion of the comparison) with the switch's MAC address (used strictly as a tiebreaker when priorities are identical). Every participating switch compares Bridge IDs, and the switch advertising the numerically lowest Bridge ID is elected root. In this exhibit, the three switches have distinctly different priority values — EX-1 at the Junos/IEEE default of 32768, EX-2 at 8192, and EX-3 at 16384 — meaning the comparison is decided entirely at the priority stage and never needs to proceed to a MAC address tiebreak at all. Since 8192 is numerically the lowest of the three priority values, EX-2 is elected root bridge purely on the strength of its lower priority, regardless of what its MAC address happens to be. This is precisely why the correct answer cites priority rather than MAC address as the deciding factor: MAC address only becomes relevant as a tiebreaker in the specific case where two or more switches share an identical priority value, which is not the situation presented here. Understanding that priority is evaluated first and is independently sufficient to decide the outcome whenever it differs is a foundational and heavily tested Spanning Tree concept on the JNCIS-ENT exam. Reference topics: Junos Enterprise Switching – Spanning Tree Protocols, Bridge ID and Root Bridge Election.

Voice VLAN is the Junos feature specifically designed to allow a single access port to simultaneously handle two distinct traffic streams: untagged data traffic from a PC or workstation using the port's normal access VLAN, and separately tagged voice traffic generated by an IP telephone that is typically daisy-chained between the switch port and the connected PC. When voice VLAN is configured on an access interface, the switch instructs the attached IP phone (commonly via LLDP-MED) which VLAN ID to tag its voice traffic with, and the switch is then able to correctly classify and prioritize that tagged voice traffic into its designated voice VLAN while simultaneously continuing to treat any untagged frames arriving on that same physical port as belonging to the port's regular, untagged access VLAN — precisely satisfying the requirement to accept both tagged and untagged traffic together on one access port. Native VLAN, by contrast, is a trunk-port-only concept that designates which VLAN untagged frames on a trunk should be associated with; it has no applicability to an access port and does not enable simultaneous tagged traffic acceptance there. Default VLAN simply refers to the VLAN an interface belongs to absent other configuration and carries no dual-traffic capability. IRB interfaces provide Layer 3 gateway functionality for a VLAN and are unrelated to how tagged versus untagged frames are accepted at Layer 2 on a given physical port. Reference topics: Junos Enterprise Switching – VLANs, Configuring Voice VLAN on Access Interfaces.

IEEE 802.3ad LACP defines two distinct negotiation modes, active and passive, and the standard's fundamental requirement for successful negotiation is that at least one end of the point-to-point link must be configured in active mode; an actively configured device initiates LACPDU transmission on its own, while a passively configured device waits and only responds once it receives an LACPDU from its peer. If both ends of the bundle were left in passive mode simultaneously, neither side would ever initiate the exchange, and no negotiation — and therefore no functioning aggregated bundle — would ever occur; at least one active participant is therefore mandatory, though having both sides active (active-active) is also fully valid and is in fact the most common production deployment. Junos does not enable LACP automatically on aggregated Ethernet interfaces; unlike some competing platforms, LACP must be explicitly configured under the aggregated-ether-options lacp hierarchy, and specifying no LACP configuration at all results in a 'static' LAG that relies purely on physical link-state rather than any protocol negotiation — there is no implicit default active mode. There is likewise no requirement to configure differing LACP system priority values between the two peer switches; system priority is used only to determine which side of the link controls port selection during negotiation and has no bearing on whether the bundle can form. Both sides being mandatorily active is a stricter requirement than the actual standard specifies. Reference topics: Junos Enterprise Switching – Link Aggregation, LACP Active and Passive Mode Negotiation.