Notes from russor: I've downloaded this driver from from https://www.silicom-usa.com/drivercat/bypass-1/ on May 31, 2022, Version 4.0.2 09/03/2021 (zip file on ftp dated Oct 19, 2021) And changed it to update the timeout/untimeout calls to callout(9) as timeout was removed from FreeBSD 13.0 and later. Interface scanning on each ioctl was removed; it was panicing on my hosts, so I switched the load time interface scanning to use ifunit_ref, added in FreeBSD 8, which I think may better handle the reasoning behind if_scan? Additionally, ifdefs allowing compilation on kernels earlier than FreeBSD 6 was removed. As a side-note, if you've got a PEG4BPI or similar, older card that shows up with vendor=0x1374, and not just the subvendor set; it might be possible to adjust the eeprom to show up with Intel vendor and device ids, and then it'll be much easier to use. The simplest way I found to do that is not super simple, but install the card in a system that can do IO-MMU based PCI passthrough to a VM; run a Linux vm, with the NIC(s) passed through with the expected Intel vendor and device id, and then you should be able to use ethtool to adjust the EEPROM. For my PEG4BPI, the desired vendor is 0x8086, device 0x105E, and Initialization Control Word 1 (Word 0Ah) needed to be adjusted, ethtool shows that word as offset 0x14 (low byte) and 0x15 (high byte); bit zero of the low byte controls whether the device uses the default vendor and device IDs or the values in the EEPROM; setting that to zero uses the default values; the device then shows up as a PEG4BPI-SD and you no longer need to modify this bpmod driver, or the em driver to detect it. Original content from Silicom below: Silicom FreeBSD Bypass Control Utility 1. Compiling, installing and loading the software. Compiling the software: # make Installing the software in the system directory: # make install Loading the driver as a dynamic module: # kldload bpmod Note: 1. To load the driver automatically when the system is booted, please compile and install the software, and, after that, edit /boot/loader.conf, and add the following line: bpmod_load="YES" 2. Please load network driver before Bypass software loading. 2. Using the software. Usage: bpctl_util <if_index|bus:slot.function> <command> [parameters] bpctl_util <info|help> <if_index> - interface name, for example, em0, or all for all Bypass-SD/TAP-SD Control devices <command> - bypass control command (see Commands List). [parameters] - set_bypass_wd command: WDT timeout interval, msec (0 for disabling WDT). set_bypass/set_bypass_pwoff/set_bypass_pwup/set_dis_bypass commands: on/off for enable/disable Bypass set_std_nic command: on/off for enable/disable Standard NIC mode set_tx command: on/off for enable/disable transmit set_tpl command: on/off for enable/disable TPL set_hw_reset command: on/off for enable/disable hw_reset set_tap/set_tap_pwup/set_dis_tap commands: on/off for enable/disable TAP set_disc/set_disc_pwup/set_dis_disc commands: on/off for enable/disable Disc set_wd_exp_mode command: bypass/tap/disc for bypass/tap/disc mode set_wd_autoreset command: WDT autoreset interval, msec (0 for disabling WDT autoreset). info - print Program Information. help - print this message. Commands List: is_bypass - check if device is a Bypass/TAP controlling device get_bypass_slave - get the second port participate in the Bypass/TAP pair get_bypass_caps - obtain Bypass/TAP capabilities information get_wd_set_caps - obtain watchdog timer settings capabilities get_bypass_info - get bypass/TAP info set_bypass - set Bypass mode state get_bypass - get Bypass mode state get_bypass_change - get change of Bypass mode state from last status check set_dis_bypass - set Disable Bypass mode get_dis_bypass - get Disable Bypass mode state set_bypass_pwoff - set Bypass mode at power-off state get_bypass_pwoff - get Bypass mode at power-off state set_bypass_pwup - set Bypass mode at power-up state get_bypass_pwup - get Bypass mode at power-up state set_std_nic - set Standard NIC mode of operation get_std_nic - get Standard NIC mode settings set_bypass_wd - set watchdog state get_bypass_wd - get watchdog state get_wd_time_expire - get watchdog expired time get_wd_expire - get watchdog expired status reset_bypass_wd - reset watchdog timer set_tx - set transmit enable / disable get_tx - get transmitter state (enabled / disabled) set_tpl - set TPL enable / disable get_tpl - get TPL state (enabled / disabled) set_hw_reset - set hw_reset enable / disable get_hw_reset - get hw_reset (enabled / disabled) set_tap - set TAP mode state get_tap - get TAP mode state get_tap_change - get change of TAP mode state from last status check set_dis_tap - set Disable TAP mode get_dis_tap - get Disable TAP mode state set_tap_pwup - set TAP mode at power-up state get_tap_pwup - get TAP mode at power-up state set_disc - set Disc mode state get_disc - get Disc mode state get_disc_change - get change of Disc mode state from last status check set_dis_disc - set Disable Disc mode get_dis_disc - get Disable Disc mode state set_disc_pwup - set Disc mode at power-up state get_disc_pwup - get Disc mode at power-up state set_wd_exp_mode - set adapter state when WDT expired get_wd_exp_mode - get adapter state when WDT expired set_wd_autoreset - set WDT autoreset mode get_wd_autoreset - get WDT autoreset mode set_bp_manuf - set manufactory default (only for 71) Example: bpctl_util em0 set_bypass_wd 5000 bpctl_util all set_bypass on bpctl_util em0 set_wd_exp_mode tap bpctl_util 0b:00.0 get_bypass_info