| "Network unreachable" errors | Network interfaces not configured | Verify netplan config and sudo netplan apply |
| SSH authentication failures | SSH keys not properly distributed | Re-run ./discover-sparks and enter passwords |
| Nodes not visible in cluster | Network connectivity issue | Verify QSFP cable connection, check IP configuration |
| "APT update" errors (eg. E: The list of sources could not be read.) | APT sources errors, conflicting sources or signing keys | Check APT and Ubuntu documentation to fix the APT sources or keys conflicts |
| NCCL test failures (eg. libnccl.so.2: cannot open shared object file) | NCCL configuration not done on all nodes | Make sure to follow the NCCL playbook to configure all nodes before running the NCCL test |
