Juniper JN0-650 Practice Test 42
Question 410
Two routers can ping each other but TCP port 179 is filtered in one direction. Which configuration or operational step BEST meets the stated requirement?
- Apply controlled AS_PATH prepending in export policy to appropriate external neighbors.
- Set a policy-based higher local preference for preferred internal BGP paths.
- Permit the intended TCP179 flow under explicit control-plane security policy.
- Allow all internet TCP ports permanently as a necessary BGP adjacency fix.
Explanation
Correct Answer
C:Permit the intended TCP179 flow under explicit control-plane security policy. BGP relies on TCP transport and does not form merely because IP reachability exists. The expected validation is that peering establishes over the authorized endpoints without opening unrelated management ports.
Incorrect Answers
A:Apply controlled AS_PATH prepending in export policy to appropriate external neighbors. This addresses BGP AS path prepend outbound advertisement rather than the required BGP TCP 179 and firewall reachability decision. BGP relies on TCP transport and does not form merely because IP reachability exists.
B:Set a policy-based higher local preference for preferred internal BGP paths. This addresses BGP LOCAL_PREF outbound exit selection rather than the required BGP TCP 179 and firewall reachability decision. BGP relies on TCP transport and does not form merely because IP reachability exists.
D:Allow all internet TCP ports permanently as a necessary BGP adjacency fix. This is a risky or ineffective shortcut for BGP TCP 179 and firewall reachability. Rejecting TCP session establishment keeps BGP Idle or Active.
Question 411
During an operational risk review, this situation is reported: Two leaf switches both start forwarding a segment intended for single-active behavior. If the underlying control is neglected, which failure would MOST directly follow?
- Different BPDU handling per VLAN can leave only some VLANs unprotected.
- Enabling unintended all-active behavior can violate a single-active attachment design.
- Lack of split-horizon handling can cause duplicate or looping flooded frames.
- Excessively broad RT import can expose tenant routes or create wrong forwarding entries.
Explanation
Correct Answer
B:Enabling unintended all-active behavior can violate a single-active attachment design. Single-active multihoming deliberately avoids parallel forwarding on a shared segment. A useful corrective investigation is to inspect active and standby Ethernet segment status during a link failover.
Incorrect Answers
A:Different BPDU handling per VLAN can leave only some VLANs unprotected. This is a VSTP interoperation and VLAN tagging failure pattern, not the primary EVPN single-active multihoming access mode failure in this case. Single-active multihoming deliberately avoids parallel forwarding on a shared segment.
C:Lack of split-horizon handling can cause duplicate or looping flooded frames. This is a EVPN multihoming split horizon loop avoidance failure pattern, not the primary EVPN single-active multihoming access mode failure in this case. Single-active multihoming deliberately avoids parallel forwarding on a shared segment.
D:Excessively broad RT import can expose tenant routes or create wrong forwarding entries. This is a EVPN route target import export scope failure pattern, not the primary EVPN single-active multihoming access mode failure in this case. Single-active multihoming deliberately avoids parallel forwarding on a shared segment.
Question 412
A third-party phone accepts network policy VLAN ID but ignores the advertised priority. Which next investigation or correction is MOST appropriate?
- Review PoE status LLDP policy tagged frames and DHCP offers from the failing port.
- Set the BGP MED attribute to 5 and expect it to become the phone's 802.1p priority.
- Inspect device class and port power negotiation counters.
- Inspect LLDP-MED network policy fields and captured 802.1Q priority bits.
Explanation
Correct Answer
D:Inspect LLDP-MED network policy fields and captured 802.1Q priority bits. This checks whether phones send frames with expected voice tags and priority values where supported.
Incorrect Answers
A:Review PoE status LLDP policy tagged frames and DHCP offers from the failing port. That check applies chiefly to IP phone first-hop diagnostic workflow, not the current LLDP-MED voice priority signaling issue. LLDP-MED can convey voice network policy including VLAN and priority information.
B:Set the BGP MED attribute to 5 and expect it to become the phone's 802.1p priority. That bypass leaves the LLDP-MED voice priority signaling issue unresolved. An incorrect priority policy can deprioritize voice even on the right VLAN.
C:Inspect device class and port power negotiation counters. That check applies chiefly to PoE class discovery and allocation, not the current LLDP-MED voice priority signaling issue. LLDP-MED can convey voice network policy including VLAN and priority information.
Question 413
A router learns one prefix from BGP and OSPF with different Junos preferences. Which configuration or operational step BEST meets the stated requirement?
- Apply controlled AS_PATH prepending in export policy to appropriate external neighbors.
- Compare Junos route preference across protocols separately from intraprotocol BGP attributes.
- Increase BGP MED and assume it necessarily beats an OSPF route in Junos RIB selection.
- Restore valid next-hop reachability without indiscriminately accepting broken routes.
Explanation
Correct Answer
B:Compare Junos route preference across protocols separately from intraprotocol BGP attributes. Junos route selection between protocols is not the same as BGP best-path selection. The expected validation is that active route reflects Junos protocol preference then applicable next-hop and policy conditions.
Incorrect Answers
A:Apply controlled AS_PATH prepending in export policy to appropriate external neighbors. This addresses BGP AS path prepend outbound advertisement rather than the required BGP route preference versus OSPF decision. Junos route selection between protocols is not the same as BGP best-path selection.
C:Increase BGP MED and assume it necessarily beats an OSPF route in Junos RIB selection. This is a risky or ineffective shortcut for BGP route preference versus OSPF. Confusing local preference with Junos route preference can produce wrong active-route reasoning.
D:Restore valid next-hop reachability without indiscriminately accepting broken routes. This addresses BGP next-hop reachability hidden route rather than the required BGP route preference versus OSPF decision. Junos route selection between protocols is not the same as BGP best-path selection.
Question 414
An application sends one stream to a 239.1.10.20 multicast group for many subscribers. Which configuration or operational step BEST meets the stated requirement?
- Troubleshoot source activity group membership RPF PIM joins and data packet counters in order.
- Distinguish multicast destination group addresses from sender unicast identities.
- Assign 239.1.10.20 as the sender interface unicast address and call it standard multicast design.
- Verify PIM join prune messages and incoming outgoing interface lists across the chain.
Explanation
Correct Answer
B:Distinguish multicast destination group addresses from sender unicast identities. IPv4 multicast destination ranges are group identifiers rather than ordinary host addresses. The expected validation is that receivers join the intended group and packets retain a valid unicast source.
Incorrect Answers
A:Troubleshoot source activity group membership RPF PIM joins and data packet counters in order. This addresses Multicast troubleshooting separate control and data planes rather than the required IPv4 multicast group address versus unicast decision. IPv4 multicast destination ranges are group identifiers rather than ordinary host addresses.
C:Assign 239.1.10.20 as the sender interface unicast address and call it standard multicast design. This is a risky or ineffective shortcut for IPv4 multicast group address versus unicast. Confusing group addresses and source addresses breaks multicast forwarding and diagnostics.
D:Verify PIM join prune messages and incoming outgoing interface lists across the chain. This addresses PIM join prune forwarding path rather than the required IPv4 multicast group address versus unicast decision. IPv4 multicast destination ranges are group identifiers rather than ordinary host addresses.
Question 415
A switch has two uplinks and one must remain blocked to prevent a Layer 2 loop. After deploying the recommended MSTP root port and alternate path change, which result MOST directly verifies success?
- Isolated endpoints reach the intended shared gateway but not peer isolated ports.
- Root and alternate ports correspond to the planned loop-free spanning tree.
- Same-community endpoints communicate while different communities stay isolated.
- A (S,G) shortest-path tree forms when supported and efficient source routing is available.
Explanation
Correct Answer
B:Root and alternate ports correspond to the planned loop-free spanning tree. This is the directly observable outcome for MSTP root port and alternate path. Spanning tree chooses port roles to avoid loops while maintaining redundant paths.
Incorrect Answers
A:Isolated endpoints reach the intended shared gateway but not peer isolated ports. This validates Private VLAN isolated port separation but does not directly demonstrate the required MSTP root port and alternate path result. Spanning tree chooses port roles to avoid loops while maintaining redundant paths.
C:Same-community endpoints communicate while different communities stay isolated. This validates Private VLAN community and promiscuous roles but does not directly demonstrate the required MSTP root port and alternate path result. Spanning tree chooses port roles to avoid loops while maintaining redundant paths.
D:A (S,G) shortest-path tree forms when supported and efficient source routing is available. This validates ASM shared tree versus SPT switchover but does not directly demonstrate the required MSTP root port and alternate path result. Spanning tree chooses port roles to avoid loops while maintaining redundant paths.
Question 416
One authorized device accidentally permits all other downstream MAC addresses. Which next investigation or correction is MOST appropriate?
- Select unrestricted port-based admission whenever there is more than one client.
- Test authorized and unauthorized MACs behind the same physical port.
- Test valid and invalid 802.1X plus MAC credentials across both endpoint classes.
- Review session timers and test role change after reauthentication.
Explanation
Correct Answer
B:Test authorized and unauthorized MACs behind the same physical port. This checks whether each permitted identity is authorized without inheriting unrelated devices' access.
Incorrect Answers
A:Select unrestricted port-based admission whenever there is more than one client. That bypass leaves the 802.1X multi-supplicant port control issue unresolved. Treating one successful login as authorization for every attached client increases exposure.
C:Test valid and invalid 802.1X plus MAC credentials across both endpoint classes. That check applies chiefly to 802.1X versus MAC RADIUS method priority, not the current 802.1X multi-supplicant port control issue. 802.1X host-mode behavior controls whether access applies per endpoint or per port.
D:Review session timers and test role change after reauthentication. That check applies chiefly to 802.1X periodic reauthentication, not the current 802.1X multi-supplicant port control issue. 802.1X host-mode behavior controls whether access applies per endpoint or per port.
Question 417
A wrong ESI on one leaf makes the access segment appear as unrelated attachments. Which technical principle BEST explains the Ethernet segment identifier ESI consistency decision?
- EVPN split-horizon prevents replication back toward the same multihomed Ethernet segment.
- Authentication success does not guarantee matching VLAN mapping or permitted data-plane access.
- ESI identifies a shared multihomed Ethernet segment to EVPN control plane.
- Type1 Ethernet A-D routes signal Ethernet segment reachability and support multihoming convergence.
Explanation
Correct Answer
C:ESI identifies a shared multihomed Ethernet segment to EVPN control plane. In this situation, the relevant action is to configure matching supported Ethernet segment identifier and multihoming attachments.
Incorrect Answers
A:EVPN split-horizon prevents replication back toward the same multihomed Ethernet segment. That principle is related to EVPN multihoming split horizon loop avoidance, not the main Ethernet segment identifier ESI consistency choice. Different ESI values on supposed peers can defeat multihoming loop protection.
B:Authentication success does not guarantee matching VLAN mapping or permitted data-plane access. That principle is related to Multiple access control enforcement troubleshooting, not the main Ethernet segment identifier ESI consistency choice. Different ESI values on supposed peers can defeat multihoming loop protection.
D:Type1 Ethernet A-D routes signal Ethernet segment reachability and support multihoming convergence. That principle is related to EVPN Type1 Ethernet auto discovery, not the main Ethernet segment identifier ESI consistency choice. Different ESI values on supposed peers can defeat multihoming loop protection.
Question 418
A broad Layer 2 tunnel unexpectedly carries provider-facing LLDP messages to a customer. Which next investigation or correction is MOST appropriate?
- Capture target control frames and verify each allowed protocol end to end.
- Inspect ingress and egress double-tag format and switch VLAN translation state.
- Check show ethernet-switching interfaces VLAN tables and tagged frame captures.
- Tunnel every provider management control packet to all customers as a safe default.
Explanation
Correct Answer
A:Capture target control frames and verify each allowed protocol end to end. This checks whether intended customer control frames cross the service without exposing provider control state.
Incorrect Answers
B:Inspect ingress and egress double-tag format and switch VLAN translation state. That check applies chiefly to QinQ service VLAN outer tag, not the current L2PT protocol selection and isolation issue. L2PT should scope control-protocol tunneling to intended customer Ethernet boundaries.
C:Check show ethernet-switching interfaces VLAN tables and tagged frame captures. That check applies chiefly to Layer 2 trunk VLAN mismatch diagnosis, not the current L2PT protocol selection and isolation issue. L2PT should scope control-protocol tunneling to intended customer Ethernet boundaries.
D:Tunnel every provider management control packet to all customers as a safe default. That bypass leaves the L2PT protocol selection and isolation issue unresolved. Overbroad tunneling may couple independent customer and provider control planes.
Question 419
A routing policy should remove one internal community before advertising externally. Select TWO statements that correctly combine the BGP communities match and deletion implementation, its evidence, or its governing principle.
- Delete the router hostname and expect BGP community attributes to disappear.
- Apply supported BGP accepted-prefix limits and operational alerts.
- Match and add or delete only documented communities using supported Junos policy statements.
- Outgoing routes retain required communities without leaking internal-only tag values.
- Export appropriate MED values where comparison conditions and policy support them.
Explanation
Correct Answers
C:Match and add or delete only documented communities using supported Junos policy statements. This is the intended implementation action for BGP communities match and deletion.
D:Outgoing routes retain required communities without leaking internal-only tag values. This is direct observable evidence for BGP communities match and deletion.
Incorrect Answers
A:Delete the router hostname and expect BGP community attributes to disappear. This would not be an appropriate BGP communities match and deletion decision. Exporting internal tags to a peer may disclose internal routing policy semantics.
B:Apply supported BGP accepted-prefix limits and operational alerts. This belongs to BGP prefix-limit peer protection, not the specified BGP communities match and deletion operation. Communities can be selectively matched manipulated and stripped in routing policy.
E:Export appropriate MED values where comparison conditions and policy support them. This belongs to BGP MED inbound traffic hint, not the specified BGP communities match and deletion operation. Communities can be selectively matched manipulated and stripped in routing policy.
Question 420
A 1-Gbps router port feeds a slower carrier subrate and queues build upstream. After deploying the recommended Junos egress shaping rate change, which result MOST directly verifies success?
- Aggregate traffic conforms to the carrier contract without unnecessary downstream discards.
- Each participating VTEP has the required BUM flood destinations for the VNI.
- Packet counters show EF-marked traffic assigned to approved forwarding class and queue.
- Bursty traffic sees acceptable loss with controlled memory usage.
Explanation
Correct Answer
A:Aggregate traffic conforms to the carrier contract without unnecessary downstream discards. This is the directly observable outcome for Junos egress shaping rate. Shaping delays packets to smooth egress rate while policing meters and may drop.
Incorrect Answers
B:Each participating VTEP has the required BUM flood destinations for the VNI. This validates EVPN Type3 IMET inclusive multicast routes but does not directly demonstrate the required Junos egress shaping rate result. Shaping delays packets to smooth egress rate while policing meters and may drop.
C:Packet counters show EF-marked traffic assigned to approved forwarding class and queue. This validates Junos ingress BA DSCP classifier but does not directly demonstrate the required Junos egress shaping rate result. Shaping delays packets to smooth egress rate while policing meters and may drop.
D:Bursty traffic sees acceptable loss with controlled memory usage. This validates Queue buffer-size allocation but does not directly demonstrate the required Junos egress shaping rate result. Shaping delays packets to smooth egress rate while policing meters and may drop.
