This article describes the following customer experience: Users connected to an access switch reported that their wired LAN connection would stop working intermittently. In the switch logs, there were real link up/down events on the affected access ports, but the interface counters did not show the usual signs of a bad switch port such as CRC, framing, FIFO, or resource errors. On one affected port, the interface showed multiple carrier transitions with zero input and output errors, and on another port the interface also showed carrier transitions with no physical-layer errors.
During the same period, the switch also logged repeated spanning-tree topology changes on the uplink and intermittent IPMC-reserved:aggregate DDoS violations. These events suggest some Layer 2 or control-plane churn in the network, but they do not prove that the switch hardware itself is faulty.
No clear Juniper hardware defect was found on the switch. The data points more to intermittent access-link instability or an endpoint-side issue, such as NIC, dock, USB Ethernet adapter, patch cable, wall jack, or another Layer 2 access condition, rather than a failed switch port. The recommended next steps are to test with a known-good cable, keep the user on one port for tracking, bypass the dock or USB adapter if possible, and continue checking the endpoint side and access path.
The spanning-tree changes and IPMC-reserved DDoS violations should still be monitored, since they may indicate broader network instability. However, based on the files reviewed, they should be treated as contributing conditions or background events, not as confirmed proof of a hardware problem on the Juniper switch.