Chapter 16. Configuring network devices to accept traffic from all MAC addresses

Network devices usually intercept and read packets that their controller is programmed to receive. You can configure the network devices to accept traffic from all MAC addresses in a virtual switch or at the port group level.

You can use this network mode to:

  • Diagnose network connectivity issues
  • Monitor network activity for security reasons
  • Intercept private data-in-transit or intrusion in the network

You can enable this mode for any kind of network device, except InfiniBand.

16.1. Temporarily configuring a device to accept all traffic

You can use the ip utility to temporary configure a network device to accept all traffic regardless of the MAC addresses.

Procedure

  1. Optional: Display the network interfaces to identify the one for which you want to receive all traffic: 

    # ip address show
1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff
...

  2. Modify the device to enable or disable this property:

    • To enable the accept-all-mac-addresses mode for enp1s0: 

      # ip link set enp1s0 promisc on

    • To disable the accept-all-mac-addresses mode for enp1s0: 

      # ip link set enp1s0 promisc off

Verification

  • Verify that the accept-all-mac-addresses mode is enabled: 

    # ip link show enp1s0
1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,PROMISC,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000
    link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff

    The PROMISC flag in the device description indicates that the mode is enabled.

16.2. Permanently configuring a network device to accept all traffic using nmcli

You can use the nmcli utility to permanently configure a network device to accept all traffic regardless of the MAC addresses.

Procedure

  1. Optional: Display the network interfaces to identify the one for which you want to receive all traffic: 

    # ip address show
1: enp1s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether 98:fa:9b:a4:34:09 brd ff:ff:ff:ff:ff:ff
...

    You can create a new connection, if you do not have any.

  2. Modify the network device to enable or disable this property.

    • To enable the ethernet.accept-all-mac-addresses mode for enp1s0: 

      # nmcli connection modify enp1s0 ethernet.accept-all-mac-addresses yes

    • To disable the accept-all-mac-addresses mode for enp1s0: 

      # nmcli connection modify enp1s0 ethernet.accept-all-mac-addresses no

  3. Apply the changes, reactivate the connection: 

    # nmcli connection up enp1s0

Verification

  • Verify that the ethernet.accept-all-mac-addresses mode is enabled: 

    # nmcli connection show enp1s0
...
802-3-ethernet.accept-all-mac-addresses:1     (true)

    The 802-3-ethernet.accept-all-mac-addresses: true indicates that the mode is enabled.

16.3. Permanently configuring a network device to accept all traffic using nmstatectl

Use the nmstatectl utility to configure a device to accept all traffic regardless of the MAC addresses through the Nmstate API. The Nmstate API ensures that, after setting the configuration, the result matches the configuration file. If anything fails, nmstatectl automatically rolls back the changes to avoid leaving the system in an incorrect state.

Prerequisites

  • The nmstate package is installed.
  • The enp1s0.yml file that you used to configure the device is available.

Procedure

  1. Edit the existing enp1s0.yml file for the enp1s0 connection and add the following content to it: 

    ---
interfaces:
  - name: enp1s0
    type: ethernet
    state: up
    accept -all-mac-address: true

    These settings configure the enp1s0 device to accept all traffic.

  2. Apply the network settings: 

    # nmstatectl apply ~/enp1s0.yml

Verification

  • Verify that the 802-3-ethernet.accept-all-mac-addresses mode is enabled: 

    # nmstatectl show enp1s0
interfaces:
  - name: enp1s0
    type: ethernet
    state: up
    accept-all-mac-addresses:     true
...

    The 802-3-ethernet.accept-all-mac-addresses: true indicates that the mode is enabled.

Additional resources

  • nmstatectl(8) man page
  • /usr/share/doc/nmstate/examples/ directory