Hey Shen!
The strange thing is that there is actually no error. The code stuck at _distributed_broadcast_coalesced and cannot be terminated by Ctrl+C.
I have tried gloo, and it works smoothly which may suggest it is not an issue related to firewall. I also have set GLOO_SOCKET_IFNAME and NCCL_SOCKET_IFNAME to the correct interface on both machine.
And for the command you suggested, it returns 127.0.1.1       icarus-Polixir on machine 1, and
fe80::b62e:99ff:fe72:d1a1 polixir-G291-Z20-00
fe80::98a3:19ff:fe05:3c61 polixir-G291-Z20-00
fe80::42:adff:fe62:bb24 polixir-G291-Z20-00
fe80::d01c:dff:fe28:8b6f polixir-G291-Z20-00
fe80::1c3d:c8ff:fe62:76cc polixir-G291-Z20-00

on machine 2. I don’t know if it’s related to the issue.