More about Cisco's USB Console Port

This past fall, I was able to work with a Cisco 1941 router, allowing me to explore the USB console in a bit more depth. Because it was the first time I've had an opportunity to work with that interface on the Cisco gear, I came to the installation process as a new user, without any previously  loaded software for this Cisco interface. This was actually beneficial, because it exposed a few other issues that might affect you if you were to approach it today.

When I first plugged the blue USB cable into my computer, nothing happened. That is, no USB device was yet detected. It appears that the USB chip in the cable gets its power from the Cisco device. Once I had the USB cable connected to the router, that's when the USB device was detected.

On a Windows 8.1 system, the USB driver is not found, and a generic interface failed to load properly, resulting in new communications. Searching the Cisco site, you will want to search for “Cisco Windows USB console driver”. The most relevant links I found work installation guides for my hardware. However, the only software download links which were still valid were dated in 2010, and the installer file for windows only supported Windows Vista, XP, and older Windows Server 2000 software.

The good news here, is that the Vista drivers included 64-bit code, and this happily installed under Windows 8.1, properly identifying the Cisco adapter as a Cypress (chip manufacturer) device,  and loaded appropriate drivers… requiring a reboot of the system.

  Device: Cypress 
  Driver added:  CiscoSerial
  Device Installed: ciscoserial.inf
  Device installed: cypressserial.inf
  Driver Management has concluded the process to add Service CiscoSerial...

On Cisco equipment which includes a USB console, there is also an LED next to the USB console interface. NOTE: When the internal interface chip is activated, this LED will illuminate, and that is a visual indication that the local RJ-45 interface has been deactivated because the USB console is active.  If the USB chip in the cable isn't initialized, the LED won't light, and the console won't be swapped.

Caution: When swapping the console channel between the RJ-45 interface and the USB interface does not alter the console process state. That is to say, if you are logged in on the RJ-45 port and already using the enabled mode, and the USB interface is activated, the USB user is now logged in and in the enabled mode!  Conversely, if you leave a session login and enabled, and then remove the USB interface, that enabled session is still now active on the RJ-45 interface. This is a strong argument for having the exec–timeout command set on your serial console line 0.

The USB serial console has a few minor differences, depending on the Cisco hardware family and IOS version. For example, not all versions will support the usb-inactivity-timeout 30 command, but this is a useful method to try and revert to the RJ-45 console, if you have a deployed console server implementation.

Swapping between RJ-45 to USB, or USB to RJ-45, does not force a logout of the consul processed. There was no visual indication (no characters received) on the RJ-45 interface which indicated that the serial process has been diverted to the USB port, or been returned to RJ-45.

 While you can connect multiple Cisco USB interfaces via a USB Hub, each Cisco device does take up a COM port on your Windows machine, or a TTY port on your Linux or OS X machine. As a result, I cannot see this as a practical method to connect the serial console for many machines in data center service. (Using the RJ-45 serial console to a console server for remote access to dozens of machines is still a much more scalable solution.) However, I think that the USB console on a Cisco product is an elegant way to use a laptop or desktop device for setup of new equipment coming in prior to deployment. It offers a quick solution for devices which only have USB interfaces, such as tablets or netbooks, to use a single cable for the configuration and quick debugging, rather than needing to support a USB-to-DE9 interface.

I am grateful for access to the 1941 ISR to be able to do this testing, and for a few candid conversations with Cisco folks who are close to the USB serial console project.