Juniper JN0-664 Exam Dumps - Valid Questions Answers

In the provided exhibit, PE-1 and PE-2 are configured with LDP-signaled pseudowires to provide Layer 2 connectivity between CE-1 and CE-2. The issue is that there is no connectivity between CE-1 and CE-2. Let’s analyze the potential causes for this fault.

1. **LDP-Signaled Pseudowire (L2 Circuit) Configuration**:

- Pseudowires in MPLS networks use LDP (Label Distribution Protocol) to signal the virtual circuit (VC) labels between PE routers.

- For successful connectivity, the VC ID (Virtual Circuit Identifier) and LSPs (Label Switched Paths) between the PE routers must be correctly configured and operational.

2. **Analysis of the Exhibit**:

- The output shows the status of the L2 circuit connection on PE-1.

- The status (St) for the interface is `rmt Dn`, which indicates that the remote site (PE-2) is down or unreachable.

3. **Potential Causes**:

- **A. The VC IDs are mismatched**:

- Correct. If the VC IDs configured on PE-1 and PE-2 do not match, the L2 circuit cannot be established. Mismatched VC IDs prevent the pseudowire from forming correctly.

- **B. There is no LSP configured from PE-1 to PE-2**:

- Correct. LSPs are required for MPLS forwarding. If there is no LSP from PE-1 to PE-2, the LDP session cannot establish a path for the pseudowire. This results in the pseudowire being down.

- **C. Interface ge-0/0/0 on PE-1 is down**:

- Incorrect. The interface status is shown as `Up`, meaning the physical interface is operational.

- **D. There is no LSP configured from PE-2 to PE-1**:

- While this might seem like a potential issue, the specific problem of the remote site being down (`rmt Dn`) typically relates more directly to the forward path from PE-1 to PE-2 (i.e., no LSP from PE-1 to PE-2). Hence, the more accurate immediate cause is covered in Option B.

**Conclusion**:

Given the analysis, the correct statements describing potential causes for the fault are:

**A. The VC IDs are mismatched.**

**B. There is no LSP configured from PE-1 to PE-2.**

**References**:

- Juniper Networks Documentation on L2 Circuits: [Configuring Layer 2 Circuits](https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/layer-2-circuits-configuring.html)

- MPLS Configuration Guide: [Juniper MPLS Configuration](https://www.juniper.net/documentation/en_US/junos/topics/topic-map/mpls-overview.html)

The correct order of packet flow through configurable components in the Junos OS CoS features is as follows:

Behavior Aggregate Classifier: This component uses a single field in a packet header to classify traffic into different forwarding classes and loss priorities based on predefined or user-defined values.

Input Policer: This component applies rate-limiting and marking actions to incoming traffic based on the forwarding class and loss priority assigned by the classifier.

Multifield Classifier: This component uses multiple fields in a packet header to classify traffic into different forwarding classes and loss priorities based on user-defined values and filters.

Forwarding Policy Options: This component applies actions such as load balancing, filtering, or routing to traffic based on the forwarding class and loss priority assigned by the classifier.

Fabric Scheduler: This component schedules traffic across the switch fabric based on the forwarding class and loss priority assigned by the classifier.

Output Policer: This component applies rate-limiting and marking actions to outgoing traffic based on the forwarding class and loss priority assigned by the classifier.

Scheduler/Shaper/RED: This component schedules, shapes, and drops traffic at the egress interface based on the forwarding class and loss priority assigned by the classifier.

Rewrite Marker: This component rewrites the code-point bits of packets leaving an interface based on the forwarding class and loss priority assigned by the classifier.

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.