Transmission caused issues with MPLS LDP establishment

ZTE and 5660 failed to establish MPLS LDP neighbor discovery between mesh points (MP)

1-Both ends can ping successfully indicating communication is possible.

2-Tracert shows direct arrival proving transmission without intermediate Layer 3 devices and no target hello involved.

3-Checking the first phase of establishment i.e. discovery phase found that ZTE debug sent hello but local end dis mpls ldp dis shows sending without receiving.

4-Capturing packets at the remote end confirmed Hello message was sent while local capture showed no hello received but received phase two session establishment request.

5-Since discovery uses multicast and session uses TCP unicast, it is suspected that there may be an issue with multicast transmission.

6-After the peer vendor dismantled the device and transported it to headquarters for direct connection with our 5660, LDP was successfully established, confirming an issue with intermediate transmission.

Replace transmission line