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Juniper JN0-664 Exam Questions
- Topic 1: OSPF: In this topic, Juniper networking professionals delve into the core concepts and operations of OSPFv2 and OSPFv3. The focus is on configuring and monitoring single-area and multi-area OSPF scenarios. This ensures proficiency in managing link-state routing protocols and enhancing network efficiency. Understanding OSPF prepares the audience to address challenges in service provider environments effectively.
- Topic 2: IS-IS: This topic provides an in-depth exploration of the Intermediate System to Intermediate System (IS-IS) protocol, focusing on its operation and concepts. Juniper networking professionals learn how to configure and monitor single-area and multi-area IS-IS, equipping them with skills essential for maintaining scalable and robust routing infrastructures in large networks.
- Topic 3: BGP: The concepts, operation, and functionality of Border Gateway Protocol (BGP) form the crux of this topic. Juniper networking professionals gain insights into BGP scaling mechanisms and develop expertise in configuring and monitoring BGP in complex scenarios. Mastery of BGP is vital for optimizing route distribution and achieving efficient inter-domain routing.
- Topic 4: Class of Service (CoS): This topic emphasizes the principles of Junos OS Class of Service (CoS). Juniper networking professionals learn to configure and monitor CoS for efficient traffic prioritization. This ensures service quality by managing bandwidth, latency, and packet loss, a critical aspect of service provider network optimization.
- Topic 5: IP Multicast: Aspiring Juniper networking professionals explore the concepts and operations of IP multicast, including IGMP, PIM dense mode, and PIM sparse mode (including SSM). The topic focuses on configuration and monitoring techniques, enabling efficient delivery of multicast traffic across the network while optimizing resource utilization.
- Topic 6: Layer 3 VPNs: This topic covers the concepts and operation of Layer 3 VPNs, including their configuration and monitoring. Juniper networking professionals also explore Junos OS support for carrier-of-carriers and inter-provider VPN models. These skills are crucial for managing secure, scalable, and interconnected multi-tenant network environments.
- Topic 7: Layer 2 VPNs: Juniper networking professionals gain comprehensive knowledge of Layer 2 VPNs, including BGP Layer 2 VPNs, LDP Layer 2 circuits, VPLS, and EVPN. This topic focuses on configuring, monitoring, and troubleshooting Layer 2 VPNs, ensuring expertise in providing efficient and seamless layer 2 connectivity across service provider networks.
Free Juniper JN0-664 Exam Actual Questions
Note: Premium Questions for JN0-664 were last updated On Aug. 13, 2025 (see below)
Exhibit
Which two statements about the output shown in the exhibit are correct? (Choose two.)
The output is from the show l2vpn connections command on a Juniper router. This command is used to verify the status of Layer 2 VPN (L2VPN) pseudowires between Provider Edge (PE) routers.
Breakdown of Key Information:
Instance: vpn-A
This is the L2VPN instance being monitored.
Connection Status (St)
The connection status is 'Up', meaning the pseudowire is operational.
Local Site: CE1-2 (2)
The PE router is attached to a single local site (CE1-2).
Uptime & Connection Flaps
The output shows the last time the connection was up:
Time last up: Apr 11 14:35:27 2020
The '# Up trans' value is 1, meaning this connection has been established once and has not flapped since it was initiated.
VLAN ID Mismatch Check
The legend includes 'VM -- VLAN ID mismatch', but this status is not present in the connection output.
This means there is NO VLAN ID mismatch.
Flow Labels
The Flow Label Transmit is No, and the Flow Label Receive is No.
This means the PE router does NOT have the capability to pop flow labels.
An interface is configured with a behavior aggregate classifier and a multifield classifier How will the packet be processed when received on this interface?
When a Juniper device receives a packet on an interface with both a Behavior Aggregate (BA) classifier and a Multifield (MF) classifier, Junos OS follows a specific processing order to apply Class of Service (CoS).
Understanding the Classifiers in Junos CoS
1 Behavior Aggregate (BA) Classifier
Uses packet headers (DSCP, IP precedence, or MPLS EXP bits) to classify traffic into forwarding classes.
Applied at the ingress interface.
Example: A packet with DSCP 46 (Expedited Forwarding) is mapped to a high-priority queue.
2 Multifield (MF) Classifier
Uses match conditions (like source/destination IP, port numbers, protocol types) to classify traffic.
Typically used for more granular classification beyond what BA can provide.
Junos Processing Order:
When both BA and MF classifiers are configured on an interface, Junos first applies the BA classifier, then the MF classifier. MF classifier can override the BA classification if necessary.
Evaluating the Answer Choices
B. The packet will be processed by the BA classifier first, then the MF classifier.
Correct, because Junos first applies BA classification based on DSCP/MPLS EXP bits.
After BA classification, the MF classifier is applied, which can refine or override the BA classification.
A. The packet will be discarded.
Incorrect, because classification does not drop packets unless explicitly configured with a filter or policing action.
C. The packet will be forwarded with no classification changes.
Incorrect, because both classifiers are applied in a specific order, meaning classification changes will occur.
D. The packet will be processed by the MF classifier first, then the BA classifier.
Incorrect, because BA classification is always applied first, followed by MF classification.
Final Answer: B. The packet will be processed by the BA classifier first, then the MF classifier.
Official Juniper Reference: 'When both BA and MF classifiers are applied on an interface, Junos OS first classifies packets using the BA classifier before applying the MF classifier.'
After a recent power outage, your manager asks you to investigate ways to automatically reduce the impact caused by suboptimal routing in your OSPF and OSPFv3 network after devices reboot.
Which three configuration statements accomplish this task? (Choose three.)
To reduce the impact of suboptimal routing in OSPF and OSPFv3 after devices reboot, you can use the overload feature to prevent a router from being used as a transit router for a specified period of time. This allows the router to stabilize its routing table before forwarding traffic for other routers. To enable the overload feature, you need to do the following:
For OSPF, configure the overload statement under [edit protocols ospf] hierarchy level. You can also specify a timeout value in seconds to indicate how long the router should remain in overload state after it boots up. For example, set protocols ospf overload timeout 900 means that the router will be in overload state for 15 minutes after it boots up.
For OSPFv3, configure the overload statement under [edit protocols ospf3] hierarchy level. You can also specify a realm (ipv4-unicast or ipv6-unicast) and a timeout value in seconds to indicate how long the router should remain in overload state after it boots up for each realm. For example, set protocols ospf3 realm ipv4-unicast overload timeout 900 means that the router will be in overload state for 15 minutes after it boots up for IPv4 unicast routing.
By default, which statement is correct about OSPF summary LSAs?
OSPF uses different types of LSAs to describe different aspects of the network topology. Type 1 LSAs are also known as router LSAs, and they describe the links and interfaces of a router within an area. Type 3 LSAs are also known as summary LSAs, and they describe routes to networks outside an area but within the same autonomous system (AS). By default, OSPF will summarize routes from Type 1 LSAs into Type 3 LSAs when advertising them across area boundaries .
In IS-IS, which two statements are correct about the designated intermediate system (DIS) on a multi-access network segment? (Choose two)
Option A (Correct):
In IS-IS, theDesignated Intermediate System (DIS)is elected based on thehighest configured priority(as defined in Junos OS).
If priorities are equal, the router with thehighest MAC addressbecomes the DIS.
A priority value of10will always override a lower priority (e.g., 1).
Option C (Correct):
On a multi-access network (e.g., Ethernet),all IS-IS routers form adjacencies with every other routeron the segment.
Unlike OSPF, IS-IS does not restrict adjacencies to only the DIS.
The DIS is responsible for creating apseudonode LSPto represent the broadcast network, but full mesh adjacencies are maintained.
Why Other Options Are Incorrect:
Option B:Incorrect. Higher priority always wins the DIS election. A priority of 1 cannot override a priority of 10.
Option D:Incorrect. IS-IS routers form adjacencies withall neighbors, not just the DIS.
Key Takeaways:
DIS Election:Prioritizes highest numerical value (e.g., 10 > 1).
Adjacency Behavior:Full mesh adjacencies are maintained, unlike OSPF.
DIS Role:Primarily for generating pseudonode LSPs and optimizing flooding, not adjacency restriction.
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