How to Identify Which Physical Port Belongs to a Network Interface in Linux

Updated: 28 September 2026 · Applies to: ethtool, iproute2 and lldpd on AlmaLinux and Rocky Linux 9 and 10, RHEL 9 and 10, Ubuntu 24.04 and 26.04, Debian 13 (physical servers)

A dedicated server with several network ports shows them as names such as eno1, eno2 or enp65s0f1. When a cable has to be moved, or a data-centre engineer needs to know which port is which, you need to match those names to the physical sockets. These methods work on physical servers; a VPS has only virtual interfaces.

1. Make the port's light blink

ethtool -p eno2 30

The LED of that port blinks for 30 seconds (press Ctrl+C to stop earlier). Someone at the server can then see which socket it is. Not every network card supports this; if nothing blinks, use the methods below.

2. Check the link and cable status

ip -br link
ethtool eno2 | grep -E 'Speed|Link detected'

Plug or unplug a cable and run the command again: the port whose "Link detected" changes is the one you touched. ip monitor link shows such changes live.

3. Hardware details: driver, PCI address and MAC

ethtool -i eno2              # driver, firmware and PCI bus address
ip link show eno2            # MAC address
ls -l /sys/class/net/        # which interface sits on which PCI device

Names like enp65s0f1 encode the PCI location: bus 65, slot 0, function 1 (on multi-port cards, usually the second port). The MAC address is often printed on a label next to the socket or listed in the server's IPMI or BMC web page.

4. Ask the switch with LLDP

Most managed switches announce their name and port number with LLDP. lldpd listens for these announcements:

apt install lldpd                                   # Ubuntu, Debian
dnf install lldpd                                   # AlmaLinux, Rocky Linux, RHEL
systemctl enable --now lldpd
lldpcli show neighbors

After about 30 seconds the output lists, for each of your interfaces, the switch name and the switch port it is plugged into. This only works if the switch has LLDP enabled.

On a Ucartz dedicated server

If you need a cable moved or a port identified in the data centre, open a support ticket with the interface name and MAC address from step 3.

Official documentation: ethtool manual page and lldpd.