DDM/DOM diagnostics, optical power, BER, link flaps, lab methods
A QSFPTEK 10GBASE-T SFP+ module installed in port ix1 of a passively cooled Netgate 6100 reported 73 C through DDM although the room was at 20 C; the module is specified for 0-70 C and up to 2.5 W. The poster asked for known-good RJ45 SFP+ modules that stay within spec. Hardware involved: Netgate…
With an Aruba 2930F connected to a server through a Stornet-branded J9283D-SN passive 3 m SFP+ DAC, port 50 dropped the link immediately after it came up and port 52 flapped with the log message FFI : Port: 52 Excessive link state transitions. The same cable worked on ports 49 and 51, and fibre…
In a NANOG discussion about vendor lock-in, an operator described two concrete failures. First, a third-party optic answered I2C reads too slowly; the switch vendor's polling code did not handle the timeout and crashed the linecard control plane, and the vendor refused to treat it as a bug because…
The poster wanted to dump the EEPROM of a QSFP+ transceiver plugged into an Intel XL710-QDA1 and ideally read live DDM values such as received optical power, as they were used to doing with SFP modules on other adapters. With i40e 2.0.23 and firmware 5.05 0x800028a2 1.1568.0, ethtool -m eth0…
On Ubuntu 18.04 (kernel 5.4.0, ethtool 5.3, i40e 2.8.20-k) the poster used 25G XXV710-based NICs bought from FS.com (FS part XXV710AM2-F2, Intel XXV710 chipset). Link and error-free wire-speed traffic worked, but reading a transceiver's DMI data with sudo ethtool -m enp4s0f0 failed with "Cannot get…
In the poster's data center several Cisco CWDM SFP/GBIC links stopped working: some ports went err-disabled (one with link-flap as the cause) and others simply showed notconnect. Troubleshooting included shut/no shut, reseating the modules, moving the CWDM SFPs to other ports, replacing the patch…
A Cisco Catalyst 3850-24XS with an SFP-10G-LR (1310 nm) connects over a single-mode cross-connect to a Tier-1 carrier's layer-2 DWDM equipment in the same data center. When the carrier shuts the circuit down, TenGigabitEthernet2/0/23 goes 'down, line protocol is down (notconnect)' yet 'show…