The default setup in #TuringPi2 #Ethernet ports can create a loop, even when the device was not on. It did create one for me and confused for a long while and mislead to multiple elsewhere(s). They are supposed to be attached to different switches by default.
"2x 1Gbps Ethernet - In bridge mode by default"
https://docs.turingpi.com/docs/turing-pi2-specs-and-io-ports
Specs and I/O Ports | Turing Pi2 | Docs
Form factor Mini ITX Dimensions 17 × 17 cm (6.7 × 6.7 in) Power Connectors Standard ATX 24 Pin socket Switch 1Gbps Switch (RTL8370MB-CG +) Data Rate 10 Mb/s, 100 Mb/s, 1 Gb/s Duplex Full Duplex, Half Duplex VLAN Support Storage Interfaces 2x SATA 3 - Standard SATA 6 connectors, up to 6Gbps per port ...