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