ethtool

Here are a few examples of ethtool use. More examples, man page.

ethtool is being supplanted by nmcli, cli to NetworkManager.

List interfaces

ip link show

Display NIC settings

root@pmox3:~# ethtool enp1s0
Settings for enp1s0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
                                2500baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
                                2500baseT/Full
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Full
        Link partner advertised pause frame use: Symmetric
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Auto-negotiation: on
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        MDI-X: Unknown
        Supports Wake-on: pumbg
        Wake-on: g
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
        Link detected: yes

Get MAC address

root@pmox2:~# ethtool -P eno1
Permanent address: 6c:2b:59:f8:0d:f6
root@pmox2:~# ethtool -P vmbr0
Permanent address: not set

Display the driver used

root@pmox2:~# ethtool -i eno1
driver: e1000e
version: 5.15.39-1-pve
firmware-version: 0.5-4
expansion-rom-version:
bus-info: 0000:00:1f.6
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: yes

root@pmox2:~# ethtool -i vmbr0
driver: bridge
version: 2.3
firmware-version: N/A
expansion-rom-version:
bus-info: N/A
supports-statistics: no
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

Display NIC statistics

Use ethtool -S enp1s0 or, better yet, watch -d "ethtool -S eno1".

root@pmox3:~# ethtool -S enp1s0
NIC statistics:
tx_packets: 12
rx_packets: 5625
tx_errors: 0
rx_errors: 0
rx_missed: 0
align_errors: 0
tx_single_collisions: 0
tx_multi_collisions: 0
unicast: 0
broadcast: 2206
multicast: 3419
tx_aborted: 0
tx_underrun: 0
tx_octets: 1694
rx_octets: 1310239
rx_multicast64: 0
tx_unicast64: 1
tx_broadcast64: 0
tx_multicast64: 11
tx_pause_on: 0
tx_pause_off: 0
tx_pause_all: 0
tx_deferred: 0
tx_late_collision: 0
tx_all_collision: 0
tx_aborted32: 0
align_errors32: 0
rx_frame_too_long: 0
rx_runt: 0
rx_pause_on: 0
rx_pause_off: 0
rx_pause_all: 0
rx_unknown_opcode: 0
rx_mac_error: 0
tx_underrun32: 0
rx_mac_missed: 0
rx_tcam_dropped: 0
tdu: 0
rdu: 0

NIC test

root@pmox3:~# ethtool -t eno1
The test result is PASS
The test extra info:
Register test (offline) 0
Eeprom test (offline) 0
Interrupt test (offline) 0
Loopback test (offline) 0
Link test (on/offline) 0

but

root@pmox3:~# ethtool -t enp1s0
Cannot test: Operation not supported

rtl8125b Connecting at 100 Mbps

alex@exi > sudo ethtool enp4s0
[sudo] password for alex:
Settings for enp4s0:
	Supported ports: [ TP	 MII ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full
	                        2500baseT/Full
	Supported pause frame use: Symmetric Receive-only
	Supports auto-negotiation: Yes
	Supported FEC modes: Not reported
	Advertised link modes:  10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full
	                        2500baseT/Full
	Advertised pause frame use: Symmetric Receive-only
	Advertised auto-negotiation: Yes
	Advertised FEC modes: Not reported
	Link partner advertised link modes:  10baseT/Half 10baseT/Full
	                                     100baseT/Half 100baseT/Full
	                                     1000baseT/Full
	Link partner advertised pause frame use: No
	Link partner advertised auto-negotiation: Yes
	Link partner advertised FEC modes: Not reported
	Speed: 100Mb/s
	Duplex: Full
	Auto-negotiation: on
	master-slave cfg: preferred slave
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: Unknown
	Supports Wake-on: pumbg
	Wake-on: g
	Link detected: yes

Trying to solve it - just unplug the ethernet cable and plug it back in. If this does not help:

# unload and reload the default kernel driver:
sudo modprobe -r r8169 && sudo modprobe r8169
# restart NetworkManager to refresh the connection:
sudo systemctl restart NetworkManager
# refresh DHCP lease
sudo dhclient -v enp4s0