BBB LAN full duplex trouble

We are facing a trouble that BBB cannot connect to our test PC via LAN cable with 100Mbps full duplex mode.
Does anyone know the solution or some information about this kind of trouble?


We are evaluating BBB to be used for a network application, which is required to connect LAN as 100Mbps full duplex mode (no auto negotiation).

We set BBB LAN to 100Mbps full duplex and connect to our test PC, but it failed to establish network link.

We should establish this connection using this test PC.

[Environment and Setting for connection test]


  1. Bootloader : U-Boot 2019.04-dirty

  2. Kernel : Linux arm 4.19.106-bone-rt-r49

  3. Root File System: Debian 10.3

Test PC

  1. Manufacturer: DELL (Vostro 14-3468)

  2. Processor : Intel® Core™ i3-6006U CPU @2.00GHz 2.00GHz

  3. RAM Capacity: 4.00GB

  4. OS: 64bit

  5. Network Card: Realtec PCIe GBE Family Controller

Network Setting


  1. IP addr:

  2. Subnet mask:

  3. Default gateway: None (


  1. IP addr:

  2. Subnet mask:

  3. Default gateway: None

Communication type

  1. 100Mbps full duplex only (both BBB and PC)

(By executing “sudo mil-tool -F 100baseTx-FD” on BBB)

  1. LAN cable: Category 5e (ELECOM)

[Detail explanation]

I booted BBB and PC with above setting, then connected LAN cable each other and got failure to establish network link – i.e. LED at RJ-45 connector on BBB didn’t light, ping command reported no connection and “dmesg | grep eth0” reported “link Down”.