Juniper JN0-352 Exam Questions

TLV 22, the Extended IS Reachability TLV defined in RFC 5305, is the modern and Junos-preferred mechanism for advertising a router's adjacent neighbors together with the metric associated with each link. It carries the seven-octet system ID and pseudonode number of each neighbor along with a 24-bit wide metric field, and supports an extensible set of sub-TLVs used for traffic-engineering data such as interface and neighbor IP addresses, bandwidth, and administrative groups. The original IS Reachability TLV, TLV 2, defined in the base ISO 10589 standard, carries similar neighbor and metric information but is constrained to a 6-bit narrow metric with a maximum value of 63, which is inadequate for expressing meaningful cost differentiation in modern, high-capacity enterprise and service-provider topologies; consequently, Junos deployments are commonly configured for wide-metrics-only, favoring TLV 22 over the legacy TLV 2 whenever traffic-engineering-capable or simply more granular metric representation is desired. TLV 132, the IP Interface Address TLV, only advertises the IPv4 addresses configured on the originating router's interfaces and carries no neighbor-adjacency or metric information. TLV 129, the Protocols Supported TLV, merely lists which network-layer protocols (such as IPv4 or IPv6) the originating router is capable of routing, and likewise has nothing to do with neighbor reachability or link cost. Reference topics: Junos Enterprise Routing -- IS-IS, Extended IS Reachability and Wide Metrics.

The intent of this filter is to match and discard traffic from one single, specific host MAC address, which requires the source-mac-address match condition to reference the complete, exact 48-bit address using an explicit /48 mask (or no mask at all, which Junos treats as an implicit full match) so that only that one precise address is matched. As configured, the term instead specifies a /40 mask on 00:12:34:56:00:07, meaning only the first 40 bits (the first five octets, 00:12:34:56:00) are actually significant to the match, while the sixth octet is effectively wildcarded across its full range; this produces an imprecise, overly broad match criterion rather than the single-host match the administrator intended, and is a common configuration mistake that undermines the predictability and correctness of MAC-based filtering. The lesson tested here is that source and destination MAC address match conditions in Junos firewall filters must be specified with the correct, deliberate, and explicit prefix length appropriate to the intended scope --- typically /48 for a single exact host --- rather than an arbitrary or miscalculated mask value. Firewall filters under family ethernet-switching are fully capable of matching on both source-mac-address and destination-mac-address, which rules out that option entirely. Layer 2 MAC-based filters function correctly on both access and trunk interface modes, so interface type is not a limiting factor here. There is no indication in the exhibit that the filter's application direction (input versus output) is reversed. Reference topics: Junos Enterprise Switching -- Layer 2 Security, MAC Address Match Conditions and Prefix Length Precision.

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.

In this configuration, R1's physical interface address (10.10.10.1) is different from the VRRP virtual IP address (10.100.100.1), meaning R1 is operating as a non-owner VRRP master --- it did not originate the virtual address as one of its own real interface addresses. By default, Junos VRRP masters that do not own the virtual address will forward transit traffic destined through that address but will not process or respond to traffic addressed directly to the VIP itself, such as ICMP echo requests, Telnet, or SSH sessions aimed at 10.100.100.1. This is deliberate default behavior intended to prevent ambiguity about which physical device is answering on behalf of a shared virtual identity. To allow the master to accept and respond to packets whose destination is the virtual address itself, the accept-data statement must be explicitly configured under the vrrp-group hierarchy. Once enabled, the elected master will process locally destined traffic sent to the VIP, resolving exactly the symptom described. The track option is used for interface or route-based priority adjustment to influence mastership, advertise-interval tunes the frequency of VRRP hello advertisements, and no-preempt prevents a higher-priority router from reclaiming mastership once a lower-priority router has taken over --- none of these affect whether the master processes traffic destined to the VIP. Reference topics: Junos Enterprise Routing -- High Availability, VRRP accept-data Behavior.