Linux: Poking the ethernet driver with the ethtool

 1. Get basic information about the interface

[mylinuxbox@mylinuxbox-linux ~]$ ethtool -i eth4
driver: e1000e
version: 2.1.4-k
firmware-version: 0.13-4
bus-info: 0000:00:19.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

2. Dump all the hardware registers

[root@mylinuxbox-linux mylinuxbox]# ethtool -d eth4
MAC Registers
-------------
0x00000: CTRL (Device control register)  0x18100240
      Endian mode (buffers):             little
      Link reset:                        normal
      Set link up:                       1
      Invert Loss-Of-Signal:             no
      Receive flow control:              enabled
      Transmit flow control:             enabled
      VLAN mode:                         disabled
      Auto speed detect:                 disabled
      Speed select:                      1000Mb/s
      Force speed:                       no
      Force duplex:                      no
0x00008: STATUS (Device status register) 0x00080083
      Duplex:                            full
      Link up:                           link config
      TBI mode:                          disabled
      Link speed:                        1000Mb/s
      Bus type:                          PCI
      Bus speed:                         33MHz
      Bus width:                         32-bit
0x00100: RCTL (Receive control register) 0x04008002
      Receiver:                          enabled
      Store bad packets:                 disabled
      Unicast promiscuous:               disabled
      Multicast promiscuous:             disabled
      Long packet:                       disabled
      Descriptor minimum threshold size: 1/2
      Broadcast accept mode:             accept
      VLAN filter:                       disabled
      Canonical form indicator:          disabled
      Discard pause frames:              filtered
      Pass MAC control frames:           don't pass
      Receive buffer size:               2048
0x02808: RDLEN (Receive desc length)     0x00001000
0x02810: RDH   (Receive desc head)       0x00000051
0x02818: RDT   (Receive desc tail)       0x00000040
0x02820: RDTR  (Receive delay timer)     0x00000000
0x00400: TCTL (Transmit ctrl register)   0x3003F0FA
      Transmitter:                       enabled
      Pad short packets:                 enabled
      Software XOFF Transmission:        disabled
      Re-transmit on late collision:     disabled
0x03808: TDLEN (Transmit desc length)    0x00001000
0x03810: TDH   (Transmit desc head)      0x0000007A
0x03818: TDT   (Transmit desc tail)      0x0000007A
0x03820: TIDV  (Transmit delay timer)    0x00000008
PHY type:                                unknown

3. Get the basic configuration of the interface

[root@mylinuxbox-linux mylinuxbox]# ethtool eth4
Settings for eth4:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 2
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: off
        Supports Wake-on: pumbg
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

4. Get important NIC statistics

 [root@mylinuxbox-linux mylinuxbox]# ethtool -S eth4

NIC statistics:
     rx_packets: 23850980
     tx_packets: 7521311
     rx_bytes: 25018525333
     tx_bytes: 867706391
     rx_broadcast: 5805854
     tx_broadcast: 14
     rx_multicast: 508810
     tx_multicast: 5
     rx_errors: 0
     tx_errors: 0
     tx_dropped: 0
     multicast: 508810
     collisions: 0
     rx_length_errors: 0
     rx_over_errors: 0
     rx_crc_errors: 0
     rx_frame_errors: 0
     rx_no_buffer_count: 0
     rx_missed_errors: 0
     tx_aborted_errors: 0
     tx_carrier_errors: 0
     tx_fifo_errors: 0
     tx_heartbeat_errors: 0
     tx_window_errors: 0
     tx_abort_late_coll: 0
     tx_deferred_ok: 0
     tx_single_coll_ok: 0
     tx_multi_coll_ok: 0
     tx_timeout_count: 0
     tx_restart_queue: 0
     rx_long_length_errors: 0
     rx_short_length_errors: 0
     rx_align_errors: 0
     tx_tcp_seg_good: 5631
     tx_tcp_seg_failed: 0
     rx_flow_control_xon: 0
     rx_flow_control_xoff: 0
     tx_flow_control_xon: 0
     tx_flow_control_xoff: 0
     rx_long_byte_count: 25018525333
     rx_csum_offload_good: 18730058
     rx_csum_offload_errors: 0
     rx_header_split: 0
     alloc_rx_buff_failed: 0
     tx_smbus: 1
     rx_smbus: 3793811
     dropped_smbus: 5276
     rx_dma_failed: 0
     tx_dma_failed: 0

5. Blink the LED of the NIC card

ethtool -p eth0

6. Make permanent changes to the NIC card

# vim /etc/network/interfaces 

post-up ethtool -s eth2 speed 1000 duplex full autoneg off