Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have an USB 3G modem (Huawei E353-u2) on pfSense 2.0.2 (which is based on FreeBSD 8.1-RELEASE-p13), it seems to create 2 /dev/cuaU devices:


1) Why are there 2 devices? Is one of them maybe the usb mass storage of the stick?

2) On the OS level (shell), how can I find out which of those 2 devices is the "real modem" / to what /dev/cuaUx.y is mapped?

Thanks for any hint :-)

share|improve this question
dmesg | grep cua tells you what? ;) . If you know the manufacturer you could grep for it too: dmesg | grep -i Huawei ... – nwildner Dec 12 '13 at 17:08

The CUA devices are both serial ports. 3G modems have often 1 to 3 serial ports. One of them is the communication port and the rest are control and monitor ports that you can use for e.g. checking the signal level (with AT commands) while connected.

The first port is almost always the communication port that you should use.

You can see if dmesg gives any hint on which port is which, but most likely only the modem knows and Huawei won't tell.

share|improve this answer

Web search suggests this modem knows AT command set, so you can easily check this using "tip" or "cu" commands with both ports and detect which one responds to AT.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.