Juniper JN0-650 Practice Test 27
Question 260
A team incorrectly configures a multicast group as the unicast source host IP. Which technical principle BEST explains the IPv4 multicast group address versus unicast decision?
- EVPN IP/MAC learning can support distributed ARP suppression where platforms support it.
- IPv4 multicast destination ranges are group identifiers rather than ordinary host addresses.
- Multicast involves host membership router tree state and actual forwarding traffic.
- IGMPv3 supports source filters needed for Source Specific Multicast participation.
Explanation
Correct Answer
B:IPv4 multicast destination ranges are group identifiers rather than ordinary host addresses. In this situation, the relevant action is to distinguish multicast destination group addresses from sender unicast identities.
Incorrect Answers
A:EVPN IP/MAC learning can support distributed ARP suppression where platforms support it. That principle is related to EVPN ARP suppression from IP MAC bindings, not the main IPv4 multicast group address versus unicast choice. Confusing group addresses and source addresses breaks multicast forwarding and diagnostics.
C:Multicast involves host membership router tree state and actual forwarding traffic. That principle is related to Multicast troubleshooting separate control and data planes, not the main IPv4 multicast group address versus unicast choice. Confusing group addresses and source addresses breaks multicast forwarding and diagnostics.
D:IGMPv3 supports source filters needed for Source Specific Multicast participation. That principle is related to IGMPv3 source include mode, not the main IPv4 multicast group address versus unicast choice. Confusing group addresses and source addresses breaks multicast forwarding and diagnostics.
Question 261
Voice queues crowd out background classes because their transmit rates are poorly planned. Which next investigation or correction is MOST appropriate?
- Measure queue throughput and share under controlled competing traffic.
- Test marked phone and PC packets against ingress queue assignment.
- Increase VLAN ID to allocate more physical bandwidth to the class.
- Review filter counters and packet classification for sample voice and data flows.
Explanation
Correct Answer
A:Measure queue throughput and share under controlled competing traffic. This checks whether congested classes meet intended minimum shares without exceeding physical bandwidth.
Incorrect Answers
B:Test marked phone and PC packets against ingress queue assignment. That check applies chiefly to QoS trust boundary at campus edge, not the current Scheduler transmit rate bandwidth allocation issue. Scheduler transmit rates allocate planned bandwidth service to queues.
C:Increase VLAN ID to allocate more physical bandwidth to the class. That bypass leaves the Scheduler transmit rate bandwidth allocation issue unresolved. Setting guaranteed transmit rates above available capacity yields unrealistic SLA expectations.
D:Review filter counters and packet classification for sample voice and data flows. That check applies chiefly to Junos multifield firewall filter classification, not the current Scheduler transmit rate bandwidth allocation issue. Scheduler transmit rates allocate planned bandwidth service to queues.
Question 262
During an operational risk review, this situation is reported: A core IGP change removes the route toward a remote BGP next-hop loopback. If the underlying control is neglected, which failure would MOST directly follow?
- Unreachable preserved eBGP next hops can make internally advertised routes unusable.
- Session Established does not guarantee the required route family was negotiated.
- Mismatched TPID assumptions can cause customer frames to be dropped.
- An accepted advertisement with an unusable next hop may not be installed.
Explanation
Correct Answer
D:An accepted advertisement with an unusable next hop may not be installed. BGP path eligibility depends on successful next-hop resolution in the routing table. A useful corrective investigation is to inspect show route hidden detail and lookup the next-hop in inet.0.
Incorrect Answers
A:Unreachable preserved eBGP next hops can make internally advertised routes unusable. This is a iBGP next-hop-self on edge failure pattern, not the primary BGP next-hop reachability hidden route failure in this case. BGP path eligibility depends on successful next-hop resolution in the routing table.
B:Session Established does not guarantee the required route family was negotiated. This is a BGP NLRI IPv4 unicast inet family failure pattern, not the primary BGP next-hop reachability hidden route failure in this case. BGP path eligibility depends on successful next-hop resolution in the routing table.
C:Mismatched TPID assumptions can cause customer frames to be dropped. This is a QinQ tag protocol EtherType compatibility failure pattern, not the primary BGP next-hop reachability hidden route failure in this case. BGP path eligibility depends on successful next-hop resolution in the routing table.
Question 263
During an operational risk review, this situation is reported: A shaper is mistakenly treated as an ingress drop-based policer. If the underlying control is neglected, which failure would MOST directly follow?
- Starving critical control-plane messages can trigger cascading route instability.
- Mis-scoped multicast can leak too far or fail to reach authorized hosts.
- An unattached scheduler map has no effect on the live bottleneck port.
- Shaping above a carrier limit can shift congestion to an uncontrolled downstream point.
Explanation
Correct Answer
D:Shaping above a carrier limit can shift congestion to an uncontrolled downstream point. Shaping delays packets to smooth egress rate while policing meters and may drop. A useful corrective investigation is to measure egress rate and queue delay during sustained load.
Incorrect Answers
A:Starving critical control-plane messages can trigger cascading route instability. This is a Network-control forwarding class differentiation failure pattern, not the primary Junos egress shaping rate failure in this case. Shaping delays packets to smooth egress rate while policing meters and may drop.
B:Mis-scoped multicast can leak too far or fail to reach authorized hosts. This is a IPv6 multicast scope and group use failure pattern, not the primary Junos egress shaping rate failure in this case. Shaping delays packets to smooth egress rate while policing meters and may drop.
C:An unattached scheduler map has no effect on the live bottleneck port. This is a Scheduler maps attached to egress interface failure pattern, not the primary Junos egress shaping rate failure in this case. Shaping delays packets to smooth egress rate while policing meters and may drop.
Question 264
A classifier places premium voice and ordinary data in the same loss priority. Which next investigation or correction is MOST appropriate?
- Gather interface CoS statistics flow captures and per-class latency before modifying rates.
- Decode outbound VLAN tag priority versus Layer 3 DSCP in packet capture.
- Set IP TTL to a high value and assume packet loss priority becomes low.
- Compare loss-priority classification and drop counters under controlled congestion.
Explanation
Correct Answer
D:Compare loss-priority classification and drop counters under controlled congestion. This checks whether congestion accounting distinguishes low-PLP and high-PLP traffic as intended.
Incorrect Answers
A:Gather interface CoS statistics flow captures and per-class latency before modifying rates. That check applies chiefly to CoS end-to-end verification of drop behavior, not the current Packet loss priority PLP marking issue. Packet loss priority influences drop likelihood independent of forwarding class alone.
B:Decode outbound VLAN tag priority versus Layer 3 DSCP in packet capture. That check applies chiefly to IEEE 802.1p CoS rewrite on Ethernet, not the current Packet loss priority PLP marking issue. Packet loss priority influences drop likelihood independent of forwarding class alone.
C:Set IP TTL to a high value and assume packet loss priority becomes low. That bypass leaves the Packet loss priority PLP marking issue unresolved. Treating every packet as identical PLP may defeat differentiated congestion policy.
Question 265
An installed handset powers up but cannot obtain an address or discover the voice VLAN. Which configuration or operational step BEST meets the stated requirement?
- Configure supported LLDP-MED voice policy with appropriate QoS marking guidance.
- Disable all VLAN separation and power policing network-wide to make one phone boot.
- Set correct voice VLAN membership and data VLAN handling for the access port.
- Diagnose PoE physical link LLDP-MED voice VLAN and DHCP stages in order.
Explanation
Correct Answer
D:Diagnose PoE physical link LLDP-MED voice VLAN and DHCP stages in order. Power negotiation Layer 2 VLAN discovery and IP addressing are separate first-hop gates. The expected validation is that each setup step is verified and the handset obtains correct network settings.
Incorrect Answers
A:Configure supported LLDP-MED voice policy with appropriate QoS marking guidance. This addresses LLDP-MED voice priority signaling rather than the required IP phone first-hop diagnostic workflow decision. Power negotiation Layer 2 VLAN discovery and IP addressing are separate first-hop gates.
B:Disable all VLAN separation and power policing network-wide to make one phone boot. This is a risky or ineffective shortcut for IP phone first-hop diagnostic workflow. Changing one DHCP option does not repair absent PoE or unsupported LLDP-MED.
C:Set correct voice VLAN membership and data VLAN handling for the access port. This addresses Voice VLAN tagged versus PC data traffic rather than the required IP phone first-hop diagnostic workflow decision. Power negotiation Layer 2 VLAN discovery and IP addressing are separate first-hop gates.
Question 266
VLAN 100 should use distribution switch A while VLAN 200 uses switch B as spanning-tree root. Which configuration or operational step BEST meets the stated requirement?
- Set explicit MSTI bridge priorities in the intended MST region.
- Configure appropriate VSTP VLAN-specific bridge priorities and port values.
- Configure compatible Multiple VLAN Registration Protocol operation on supported links.
- Use identical MST region mapping as a substitute for configuring all required VSTP per-VLAN roots.
Explanation
Correct Answer
B:Configure appropriate VSTP VLAN-specific bridge priorities and port values. VSTP runs per-VLAN spanning-tree decisions rather than one shared instance. The expected validation is that each VLAN shows its intended root and a loop-free active topology.
Incorrect Answers
A:Set explicit MSTI bridge priorities in the intended MST region. This addresses MSTP instance root selection rather than the required VSTP per-VLAN root distribution decision. VSTP runs per-VLAN spanning-tree decisions rather than one shared instance.
C:Configure compatible Multiple VLAN Registration Protocol operation on supported links. This addresses MVRP dynamic VLAN registration rather than the required VSTP per-VLAN root distribution decision. VSTP runs per-VLAN spanning-tree decisions rather than one shared instance.
D:Use identical MST region mapping as a substitute for configuring all required VSTP per-VLAN roots. This is a risky or ineffective shortcut for VSTP per-VLAN root distribution. Misconfigured VLAN-specific roots can send traffic over inefficient links.
Question 267
A routed link stays in Two-Way instead of Full and the operator suspects failure. Which configuration or operational step BEST meets the stated requirement?
- Align supported MTU and OSPF adjacency expectations on the link.
- Clear every routing daemon whenever any OSPF neighbor displays Two-Way.
- Interpret neighbor state relative to network type and compare timers MTU and authentication.
- Verify IPv6 interface participation and OSPFv3 prefix advertisement settings.
Explanation
Correct Answer
C:Interpret neighbor state relative to network type and compare timers MTU and authentication. Two-Way may be normal between DROther neighbors while Exchange stuck indicates database issues. The expected validation is that expected adjacency relationships achieve correct state for the selected network type.
Incorrect Answers
A:Align supported MTU and OSPF adjacency expectations on the link. This addresses OSPF interface MTU mismatch rather than the required OSPF neighbor state troubleshooting workflow decision. Two-Way may be normal between DROther neighbors while Exchange stuck indicates database issues.
B:Clear every routing daemon whenever any OSPF neighbor displays Two-Way. This is a risky or ineffective shortcut for OSPF neighbor state troubleshooting workflow. Treating every Two-Way adjacency as a fatal database synchronization failure causes unnecessary changes.
D:Verify IPv6 interface participation and OSPFv3 prefix advertisement settings. This addresses OSPFv3 IPv6 prefix advertisement rather than the required OSPF neighbor state troubleshooting workflow decision. Two-Way may be normal between DROther neighbors while Exchange stuck indicates database issues.
Question 268
Distribution links show VLAN membership configured but only one side tagged the relevant VLAN. Select TWO statements that correctly combine the Layer 2 trunk VLAN mismatch diagnosis implementation, its evidence, or its governing principle.
- Combine required static VLAN membership with deliberate dynamic registration policy.
- Trace each Layer 2 hop for VLAN membership tagging outer and inner tags and protection state.
- Globally disable all spanning-tree and VLAN filters to make one service appear reachable.
- Validate compatible VSTP participation per VLAN and consistent trunk membership.
- End-to-end captures preserve intended VLAN identity and forwarding without unapproved leakage.
Explanation
Correct Answers
B:Trace each Layer 2 hop for VLAN membership tagging outer and inner tags and protection state. This is the intended implementation action for Layer 2 trunk VLAN mismatch diagnosis.
E:End-to-end captures preserve intended VLAN identity and forwarding without unapproved leakage. This is direct observable evidence for Layer 2 trunk VLAN mismatch diagnosis.
Incorrect Answers
A:Combine required static VLAN membership with deliberate dynamic registration policy. This belongs to MVRP static versus dynamic registration, not the specified Layer 2 trunk VLAN mismatch diagnosis operation. VLAN delivery requires consistent port roles tags and eligible forwarding state at every hop.
C:Globally disable all spanning-tree and VLAN filters to make one service appear reachable. This would not be an appropriate Layer 2 trunk VLAN mismatch diagnosis decision. Troubleshooting only end-host IP routes can miss a transport VLAN mismatch.
D:Validate compatible VSTP participation per VLAN and consistent trunk membership. This belongs to VSTP interoperation and VLAN tagging, not the specified Layer 2 trunk VLAN mismatch diagnosis operation. VLAN delivery requires consistent port roles tags and eligible forwarding state at every hop.
Question 269
A visitor laptop without an enterprise supplicant must receive only limited guest connectivity. After deploying the recommended Guest VLAN for unauthenticated clients change, which result MOST directly verifies success?
- Guests receive only allowed connectivity and protected subnets stay unreachable.
- Session logs identify the failing exchange or authorized role without broad policy bypass.
- Intended customer control frames cross the service without exposing provider control state.
- New identity policy takes effect without repeatedly disrupting healthy clients.
Explanation
Correct Answer
A:Guests receive only allowed connectivity and protected subnets stay unreachable. This is the directly observable outcome for Guest VLAN for unauthenticated clients. Guest VLAN authorizes limited access for eligible unauthenticated clients.
Incorrect Answers
B:Session logs identify the failing exchange or authorized role without broad policy bypass. This validates Junos Layer 2 authentication session monitoring but does not directly demonstrate the required Guest VLAN for unauthenticated clients result. Guest VLAN authorizes limited access for eligible unauthenticated clients.
C:Intended customer control frames cross the service without exposing provider control state. This validates L2PT protocol selection and isolation but does not directly demonstrate the required Guest VLAN for unauthenticated clients result. Guest VLAN authorizes limited access for eligible unauthenticated clients.
D:New identity policy takes effect without repeatedly disrupting healthy clients. This validates 802.1X periodic reauthentication but does not directly demonstrate the required Guest VLAN for unauthenticated clients result. Guest VLAN authorizes limited access for eligible unauthenticated clients.
Question 270
Two switches with identical MST instance IDs operate as different MST regions. Which configuration or operational step BEST meets the stated requirement?
- Change the BGP local AS to make mismatched MST region digests agree.
- Align MSTP region name revision and VLAN-to-instance mapping across intended peers.
- Configure supported Layer 2 Protocol Tunneling for selected customer control protocols.
- Tune approved MST port costs and priorities based on the intended topology.
Explanation
Correct Answer
B:Align MSTP region name revision and VLAN-to-instance mapping across intended peers. MST region identity depends on matching region attributes including VLAN mapping digest. The expected validation is that switches report the same MST region and shared MSTI topology.
Incorrect Answers
A:Change the BGP local AS to make mismatched MST region digests agree. This is a risky or ineffective shortcut for MSTP region name revision and VLAN digest. Slight configuration mismatches can create independent MST regions and unexpected port states.
C:Configure supported Layer 2 Protocol Tunneling for selected customer control protocols. This addresses L2PT customer BPDU tunneling rather than the required MSTP region name revision and VLAN digest decision. MST region identity depends on matching region attributes including VLAN mapping digest.
D:Tune approved MST port costs and priorities based on the intended topology. This addresses MSTP root port and alternate path rather than the required MSTP region name revision and VLAN digest decision. MST region identity depends on matching region attributes including VLAN mapping digest.
