Juniper JN0-650 Practice Test 20
Question 190
A dual-stack branch forms IPv4 OSPF neighbors but IPv6 route propagation remains broken. Which technical principle BEST explains the OSPFv2 versus OSPFv3 operations decision?
- OSPFv2 and OSPFv3 have related SPF logic but separate protocol and address-family configuration.
- OSPF DR election on broadcast networks is priority based and nonpreemptive under normal conditions.
- OSPF stub areas restrict external AS-external advertisements and require compatible area flags.
- Guest VLAN authorizes limited access for eligible unauthenticated clients.
Explanation
Correct Answer
A:OSPFv2 and OSPFv3 have related SPF logic but separate protocol and address-family configuration. In this situation, the relevant action is to troubleshoot OSPF and OSPFv3 sessions and tables as distinct address-family contexts.
Incorrect Answers
B:OSPF DR election on broadcast networks is priority based and nonpreemptive under normal conditions. That principle is related to OSPF designated router election broadcast LAN, not the main OSPFv2 versus OSPFv3 operations choice. A healthy IPv4 neighbor is not proof of IPv6 adjacency or prefix reachability.
C:OSPF stub areas restrict external AS-external advertisements and require compatible area flags. That principle is related to OSPF stub area external LSA suppression, not the main OSPFv2 versus OSPFv3 operations choice. A healthy IPv4 neighbor is not proof of IPv6 adjacency or prefix reachability.
D:Guest VLAN authorizes limited access for eligible unauthenticated clients. That principle is related to Guest VLAN for unauthenticated clients, not the main OSPFv2 versus OSPFv3 operations choice. A healthy IPv4 neighbor is not proof of IPv6 adjacency or prefix reachability.
Question 191
A dual-homed access design shows repeated broadcast traffic after adding a second EVPN peer. Select TWO statements that correctly combine the EVPN multihoming split horizon loop avoidance implementation, its evidence, or its governing principle.
- Disable all ESI-aware forwarding checks so every flooded packet is replicated to all ports.
- Validate EVPN Type3 inclusive multicast route advertisement and remote replication lists.
- Enforce supported ESI split-horizon handling and verify multihomed replication behavior.
- Configure matching supported Ethernet segment identifier and multihoming attachments.
- BUM frames are not looped back to the originating Ethernet segment.
Explanation
Correct Answers
C:Enforce supported ESI split-horizon handling and verify multihomed replication behavior. This is the intended implementation action for EVPN multihoming split horizon loop avoidance.
E:BUM frames are not looped back to the originating Ethernet segment. This is direct observable evidence for EVPN multihoming split horizon loop avoidance.
Incorrect Answers
A:Disable all ESI-aware forwarding checks so every flooded packet is replicated to all ports. This would not be an appropriate EVPN multihoming split horizon loop avoidance decision. Lack of split-horizon handling can cause duplicate or looping flooded frames.
B:Validate EVPN Type3 inclusive multicast route advertisement and remote replication lists. This belongs to EVPN Type3 IMET inclusive multicast routes, not the specified EVPN multihoming split horizon loop avoidance operation. EVPN split-horizon prevents replication back toward the same multihomed Ethernet segment.
D:Configure matching supported Ethernet segment identifier and multihoming attachments. This belongs to Ethernet segment identifier ESI consistency, not the specified EVPN multihoming split horizon loop avoidance operation. EVPN split-horizon prevents replication back toward the same multihomed Ethernet segment.
Question 192
An ABR advertises thousands of adjacent site networks and operators want a smaller summary. Which configuration or operational step BEST meets the stated requirement?
- Apply supported route policy at the correct Junos OSPF import or RIB-selection control.
- Apply a correct address-range summary on the intended ABR with covering-prefix review.
- Configure each access switch as a BGP route reflector to summarize OSPF areas.
- Restore valid area 0 backbone connectivity and supported ABR relationships.
Explanation
Correct Answer
B:Apply a correct address-range summary on the intended ABR with covering-prefix review. OSPF interarea summarization originates at area boundaries with reachability tradeoffs. The expected validation is that other areas see the approved aggregate while required specifics remain reachable.
Incorrect Answers
A:Apply supported route policy at the correct Junos OSPF import or RIB-selection control. This addresses OSPF routing policy import filtering rather than the required OSPF interarea route summarization decision. OSPF interarea summarization originates at area boundaries with reachability tradeoffs.
C:Configure each access switch as a BGP route reflector to summarize OSPF areas. This is a risky or ineffective shortcut for OSPF interarea route summarization. Overly broad summaries can attract traffic to absent component prefixes.
D:Restore valid area 0 backbone connectivity and supported ABR relationships. This addresses OSPF area-border backbone connectivity rather than the required OSPF interarea route summarization decision. OSPF interarea summarization originates at area boundaries with reachability tradeoffs.
Question 193
During an operational risk review, this situation is reported: A shared printer moves ports and the security policy denies its MAC credentials. If the underlying control is neglected, which failure would MOST directly follow?
- Treating Access-Reject as the same failure as timeout can trigger unsafe fallback behavior.
- Treating a MAC address as strong cryptographic proof can weaken segmentation.
- Placing critical admin endpoints behind MAC-only authentication permits spoofing risk.
- An overly general term can prevent subsequent protective terms from being reached.
Explanation
Correct Answer
B:Treating a MAC address as strong cryptographic proof can weaken segmentation. MAC RADIUS can authorize nonsupplicant devices but MAC identity is easier to spoof. A useful corrective investigation is to review MAC authorization records and test denied unknown device.
Incorrect Answers
A:Treating Access-Reject as the same failure as timeout can trigger unsafe fallback behavior. This is a RADIUS Access-Accept versus Access-Reject handling failure pattern, not the primary MAC RADIUS printer onboarding failure in this case. MAC RADIUS can authorize nonsupplicant devices but MAC identity is easier to spoof.
C:Placing critical admin endpoints behind MAC-only authentication permits spoofing risk. This is a MAC RADIUS spoofing limitations failure pattern, not the primary MAC RADIUS printer onboarding failure in this case. MAC RADIUS can authorize nonsupplicant devices but MAC identity is easier to spoof.
D:An overly general term can prevent subsequent protective terms from being reached. This is a Junos BGP policy term matching failure pattern, not the primary MAC RADIUS printer onboarding failure in this case. MAC RADIUS can authorize nonsupplicant devices but MAC identity is easier to spoof.
Question 194
A carrier-prepend policy makes one available route look less attractive to remote ASes. Which technical principle BEST explains the BGP AS_PATH loop prevention and length decision?
- Junos routing policy evaluates ordered terms and control-flow actions.
- BGP AS_PATH records AS traversal and participates in loop prevention and path selection.
- MED is a nontransitive path attribute often compared between paths from the same neighboring AS.
- Multiple authentication methods must be composed without creating a bypass path.
Explanation
Correct Answer
B:BGP AS_PATH records AS traversal and participates in loop prevention and path selection. In this situation, the relevant action is to use deliberate AS-path policy without bypassing loop-prevention safeguards.
Incorrect Answers
A:Junos routing policy evaluates ordered terms and control-flow actions. That principle is related to Junos BGP policy term matching, not the main BGP AS_PATH loop prevention and length choice. Ignoring the local-AS loop check can introduce unstable routing behavior.
C:MED is a nontransitive path attribute often compared between paths from the same neighboring AS. That principle is related to BGP MED inbound traffic hint, not the main BGP AS_PATH loop prevention and length choice. Ignoring the local-AS loop check can introduce unstable routing behavior.
D:Multiple authentication methods must be composed without creating a bypass path. That principle is related to 802.1X versus MAC RADIUS method priority, not the main BGP AS_PATH loop prevention and length choice. Ignoring the local-AS loop check can introduce unstable routing behavior.
Question 195
A route carrying the local ASN is received from a transit peer and is rejected. Which configuration or operational step BEST meets the stated requirement?
- Use deliberate AS-path policy without bypassing loop-prevention safeguards.
- Remove all route-target communities and claim an AS_PATH loop has been resolved.
- Configure supported route reflector clients and cluster identifiers with loop safeguards.
- Enable compatible inet-unicast family capabilities and correct routing policies.
Explanation
Correct Answer
A:Use deliberate AS-path policy without bypassing loop-prevention safeguards. BGP AS_PATH records AS traversal and participates in loop prevention and path selection. The expected validation is that selected routes have expected AS sequence and no local-AS loop.
Incorrect Answers
B:Remove all route-target communities and claim an AS_PATH loop has been resolved. This is a risky or ineffective shortcut for BGP AS_PATH loop prevention and length. Ignoring the local-AS loop check can introduce unstable routing behavior.
C:Configure supported route reflector clients and cluster identifiers with loop safeguards. This addresses BGP route reflection cluster rather than the required BGP AS_PATH loop prevention and length decision. BGP AS_PATH records AS traversal and participates in loop prevention and path selection.
D:Enable compatible inet-unicast family capabilities and correct routing policies. This addresses BGP NLRI IPv4 unicast inet family rather than the required BGP AS_PATH loop prevention and length decision. BGP AS_PATH records AS traversal and participates in loop prevention and path selection.
Question 196
A newly installed summary route changes the RPF interface for a heavily used group. Which technical principle BEST explains the Multicast source route policy and RPF decision?
- IGMP expresses host interest in groups while routing protocols move traffic between subnets.
- RPF uses source or RP reachability and can change when unicast routing changes.
- A policer meters traffic and may drop or remark traffic exceeding its limits.
- IGMP snooping uses observed host joins to constrain layer-2 multicast replication.
Explanation
Correct Answer
B:RPF uses source or RP reachability and can change when unicast routing changes. In this situation, the relevant action is to align source reachability and any approved multicast RPF policy with actual topology.
Incorrect Answers
A:IGMP expresses host interest in groups while routing protocols move traffic between subnets. That principle is related to IGMPv2 membership report and leave, not the main Multicast source route policy and RPF choice. An unexpected source route preference may cause RPF failures after a control-plane change.
C:A policer meters traffic and may drop or remark traffic exceeding its limits. That principle is related to Junos ingress policer rate limit, not the main Multicast source route policy and RPF choice. An unexpected source route preference may cause RPF failures after a control-plane change.
D:IGMP snooping uses observed host joins to constrain layer-2 multicast replication. That principle is related to IGMP snooping access-port replication, not the main Multicast source route policy and RPF choice. An unexpected source route preference may cause RPF failures after a control-plane change.
Question 197
During an operational risk review, this situation is reported: A new authentication policy is installed yet active endpoint sessions retain old roles. If the underlying control is neglected, which failure would MOST directly follow?
- Failure to reauthorize after recovery can leave endpoints overprivileged or stuck in fallback.
- Treating one successful login as authorization for every attached client increases exposure.
- Assuming all ASM traffic must stay permanently on RP shared tree may waste bandwidth.
- Excessively short reauthentication periods can destabilize normal connectivity.
Explanation
Correct Answer
A:Failure to reauthorize after recovery can leave endpoints overprivileged or stuck in fallback. Server-recovery behavior and authentication session lifecycle affect effective access. A useful corrective investigation is to inspect authenticator sessions and RADIUS logs before and after service restoration.
Incorrect Answers
B:Treating one successful login as authorization for every attached client increases exposure. This is a 802.1X multi-supplicant port control failure pattern, not the primary RADIUS server-fail remediation and reauthentication failure in this case. Server-recovery behavior and authentication session lifecycle affect effective access.
C:Assuming all ASM traffic must stay permanently on RP shared tree may waste bandwidth. This is a ASM shared tree versus SPT switchover failure pattern, not the primary RADIUS server-fail remediation and reauthentication failure in this case. Server-recovery behavior and authentication session lifecycle affect effective access.
D:Excessively short reauthentication periods can destabilize normal connectivity. This is a 802.1X periodic reauthentication failure pattern, not the primary RADIUS server-fail remediation and reauthentication failure in this case. Server-recovery behavior and authentication session lifecycle affect effective access.
Question 198
A migrated access switch tags ordinary endpoint frames that expect untagged delivery. Which technical principle BEST explains the Ethernet access interface VLAN membership decision?
- Per-VLAN STP compatibility depends on VLAN tagging and protocol expectations.
- Access VLAN membership maps untagged endpoint traffic into one logical broadcast domain.
- Single-active multihoming deliberately avoids parallel forwarding on a shared segment.
- IEEE 802.1Q tags distinguish VLAN traffic across a common trunk.
Explanation
Correct Answer
B:Access VLAN membership maps untagged endpoint traffic into one logical broadcast domain. In this situation, the relevant action is to set supported access interface VLAN membership for the intended user segment.
Incorrect Answers
A:Per-VLAN STP compatibility depends on VLAN tagging and protocol expectations. That principle is related to VSTP interoperation and VLAN tagging, not the main Ethernet access interface VLAN membership choice. Changing the switch IP address does not correct an endpoint access VLAN mismatch.
C:Single-active multihoming deliberately avoids parallel forwarding on a shared segment. That principle is related to EVPN single-active multihoming access mode, not the main Ethernet access interface VLAN membership choice. Changing the switch IP address does not correct an endpoint access VLAN mismatch.
D:IEEE 802.1Q tags distinguish VLAN traffic across a common trunk. That principle is related to 802.1Q trunk allowed VLANs, not the main Ethernet access interface VLAN membership choice. Changing the switch IP address does not correct an endpoint access VLAN mismatch.
Question 199
A switch port still uses default queues after a custom scheduler map is created. Which technical principle BEST explains the Scheduler maps attached to egress interface decision?
- A CoS trust boundary defines whose markings should be honored.
- Network-control traffic may need separate protection from bulk and voice services.
- Scheduler maps associate forwarding classes with schedulers and require interface application.
- VXLAN data plane depends on routable VTEP endpoints independent of EVPN MAC learning.
Explanation
Correct Answer
C:Scheduler maps associate forwarding classes with schedulers and require interface application. In this situation, the relevant action is to apply the intended scheduler map to the actual output interface.
Incorrect Answers
A:A CoS trust boundary defines whose markings should be honored. That principle is related to QoS trust boundary at campus edge, not the main Scheduler maps attached to egress interface choice. An unattached scheduler map has no effect on the live bottleneck port.
B:Network-control traffic may need separate protection from bulk and voice services. That principle is related to Network-control forwarding class differentiation, not the main Scheduler maps attached to egress interface choice. An unattached scheduler map has no effect on the live bottleneck port.
D:VXLAN data plane depends on routable VTEP endpoints independent of EVPN MAC learning. That principle is related to VXLAN VTEP loopback underlay route, not the main Scheduler maps attached to egress interface choice. An unattached scheduler map has no effect on the live bottleneck port.
Question 200
During an operational risk review, this situation is reported: A forwarding class has correct scheduling but packet captures show wrong outbound markings. If the underlying control is neglected, which failure would MOST directly follow?
- Assuming IP DSCP automatically sets all Ethernet priority bits causes inconsistencies.
- An overly permissive guest VLAN becomes an alternative corporate-network entry.
- Ingress classification does not itself guarantee downstream marking consistency.
- Excessively small buffers cause avoidable drops while overlarge buffers increase delay.
Explanation
Correct Answer
C:Ingress classification does not itself guarantee downstream marking consistency. Junos rewrite rules use internal forwarding class and PLP to set outbound header bits. A useful corrective investigation is to inspect rewrite rule binding and compare inbound versus outbound DSCP captures.
Incorrect Answers
A:Assuming IP DSCP automatically sets all Ethernet priority bits causes inconsistencies. This is a IEEE 802.1p CoS rewrite on Ethernet failure pattern, not the primary DSCP egress rewrite rules failure in this case. Junos rewrite rules use internal forwarding class and PLP to set outbound header bits.
B:An overly permissive guest VLAN becomes an alternative corporate-network entry. This is a Guest VLAN for unauthenticated clients failure pattern, not the primary DSCP egress rewrite rules failure in this case. Junos rewrite rules use internal forwarding class and PLP to set outbound header bits.
D:Excessively small buffers cause avoidable drops while overlarge buffers increase delay. This is a Queue buffer-size allocation failure pattern, not the primary DSCP egress rewrite rules failure in this case. Junos rewrite rules use internal forwarding class and PLP to set outbound header bits.
