Provided by: freebsd-manpages_12.2-1_all bug


     cdce — USB Communication Device Class Ethernet (CDC ECM/NCM) driver


     To compile this driver into the kernel, place the following lines in your kernel
     configuration file:

           device uhci
           device ohci
           device usb
           device miibus
           device uether
           device cdce

     Alternatively, to load the driver as a module at boot time, place the following line in



     The cdce driver provides support for USB Host-to-Host (aka USB-to-USB) and USB-to-Ethernet
     bridges based on the USB Communication Device Class Ethernet Control Model (CDC ECM) and
     Network Control Model (CDC NCM) specifications.  It also provides device-side CDC ECM

     The USB bridge appears as a regular network interface on both sides, transporting Ethernet

     For more information on configuring this device, see ifconfig(8).

     USB 1.x bridges support speeds of up to 12Mbps, and USB 2.0 speeds of up to 480Mbps.

     Packets are received and transmitted over separate USB bulk transfer endpoints.

     The cdce driver does not support different media types or options.


     The following devices are supported by the cdce driver:

        Prolific PL-2501 Host-to-Host Bridge Controller
        Sharp Zaurus PDA
        Terayon TJ-715 DOCSIS Cable Modem


     cdce%d: no union descriptor  The driver could not fetch an interface descriptor from the USB
     device.  For a manually added USB vendor/product, the CDCE_NO_UNION flag can be tried to
     work around the missing descriptor.

     cdce%d: no data interface
     cdce%d: could not read endpoint descriptor
     cdce%d: unexpected endpoint
     cdce%d: could not find data bulk in/out  For a manually added USB vendor/product, these
     errors indicate that the bridge is not compatible with the driver.

     cdce%d: watchdog timeout  A packet was queued for transmission and a transmit command was
     issued, however the device failed to acknowledge the transmission before a timeout expired.

     cdce%d: no memory for rx list -- packet dropped!  Memory allocation through MGETHDR or
     MCLGET failed, the system is running low on mbufs.

     cdce%d: abort/close rx/tx pipe failed
     cdce%d: rx/tx list init failed
     cdce%d: open rx/tx pipe failed
     cdce%d: usb error on rx/tx


     arp(4), cdceem(4), intro(4), ipheth(4), netintro(4), urndis(4), usb(4), ifconfig(8)

     Universal Serial Bus Class Definitions for Communication Devices,

     Data sheet Prolific PL-2501 Host-to-Host Bridge/Network Controller,


     The cdce device driver first appeared in OpenBSD 3.6, NetBSD 3.0 and FreeBSD 6.0.


     The cdce driver was written by Craig Boston <> based on the aue(4)
     driver written by Bill Paul <> and ported to OpenBSD by Daniel Hartmeier


     Many USB devices notoriously fail to report their class and interfaces correctly.
     Undetected products might work flawlessly when their vendor and product IDs are added to the
     driver manually.