A quick plain-English guide to the interface names you'll see on an EVE-OS device.

When EVE-OS boots, every physical NIC on the box gets discovered and given a name based on PCI location (like eth0, eth1, etc). These are your physical ports, the actual copper/fiber jacks on the hardware.

• eth0 is what everything in EVE and your apps expect to see: the IP address, VLAN subinterfaces, DHCP lease, all of it.
• What's actually behind that name depends on the port. Read on.

This is the one that confuses people, because it shows up even with zero Switch NIs configured.

• EVE puts a Linux bridge in front of nearly every Ethernet port it manages. Not just ports used by a Switch NI, basically all of them.
• The exceptions: LTE and WiFi ports (can't do Ethernet bridging), and ports that are members of a VLAN or bond adapter (those skip the kethX treatment).
• Why bridge everything up front: so a bridge is already sitting there ready to accept app VIFs later, even on the management port itself, without needing a reboot or reconfig.
• To pull this off without renaming anything visible, EVE renames the physical NIC to kethX and lets the bridge take over the eth0 name.

• EVE 17.0 and newer (PR #6167, merged Jul 2026): ethX and kethX share the exact same MAC address. Testing showed this causes no problems; the Linux bridge FDB tolerates a duplicate local address by design, and NIM only assigns IP (including IPv6 link-local) to the ethX bridge, never to kethX, so there's no collision.
• Older EVE (pre-17.0, still true on 16.0/14.5/13.4-stable): kethX got a different MAC than ethX by flipping the locally-administered bit. This was a conservative design choice, not a technical requirement, and it's what could make a box look like it has two MACs on one port, which some security software flagged.
• Check your EVE version before assuming which behavior you're looking at.

• These are the bridges you create explicitly through Switch NI or Local NI configuration.
• Different from the invisible per-port bridge described above. NI bridges are user-visible and app VIFs attach to them directly.
• Local NI adds NAT, DHCP, and DNS on top. Switch NI is pure L2.

• lf-edge EVE design doc “K3S flat network in EVE” (wiki.lfedge.org), original bridge-per-port and keth renaming design.
• lf-edge/eve PR #6167, “dpcreconciler: drop alternativeMAC”, merged Jul 17 2026, backported to 17.0. Confirms current MAC-sharing behavior and drops the old locally-administered-bit distinction.