Arista EOS Configuration and Operations
Core concepts
EOS is a single-image, Linux-based network OS with a SysDB architecture and a consistent CLI across platforms. Know the operational modes: enable, configure, and interface/config submodes. Master the show command family: show running-config, show interfaces, show ip route, show lldp neighbors, show vlan, and show spanning-tree. Understand configuration persistence - running-config vs startup-config - and the copy/commit workflow.
Concepts to master
Management access (eAPI, SSH, AAA), user roles, and the difference between reload and reload now. Know how to read interface counters (input/output errors, CRC, runts), how to verify link state and speed, and how to use show logging and show tech-support for escalation. Understand MLAG verification commands (show mlag, show mlag interfaces) and VXLAN/VTEP verification (show vxlan vtep, show vxlan address-table).
Traps
Questions often test whether a change is saved: editing running-config does not persist across reload unless written to startup-config. Another trap is confusing show interfaces status (summary) with show interfaces (detailed counters). Watch for questions implying EOS requires per-feature licenses at the CLI level - the CLI is uniform; licensing is separate.
Worked example
A server link flaps. Run show interfaces Ethernet1 to check link state, speed/duplex, and error counters. High CRC/input errors point to cabling or optics; clean counters but no traffic point to VLAN or STP state. Confirm with show interfaces status and show lldp neighbors to validate the peer.