Devices with only USB console port - Need a Console Server Solution

Jared Mauch jared at
Tue Feb 2 21:12:16 UTC 2016

> On Feb 2, 2016, at 3:56 PM, William Herrin <bill at> wrote:
> On Tue, Feb 2, 2016 at 9:11 AM, Jared Mauch <jared at> wrote:
>>        Yes, but I'm always concerned about what boot messages are lost
>> or things you can't quite do properly (like send break, etc) to get into
>> the device as you're waiting for the USB to initalize, driver to present
>> to OS, etc..  Maybe they spent more time thinking about this than I
>> am aware, but it's something I've not had a proper solution explained to me
>> for.
> Hi Jared,
> Like all USB to serial adapters, the the USB port on the router is
> powered by the laptop or whatever device it's plugged in to. It
> initializes and is ready before you turn the router on.
> I have not had any problems sending a serial break via USB-to-serial
> adapters. Have you?


I’ve had a lot of issues with various USB serial devices and proper
support.  There’s a lot of cheap windows only hardware out there.

> You can get a server in a shallow-depth 1U case with a solid state
> drive just as readily as a serial console server. Add USB ports and
> hubs. This gives you a Linux box on site (handy for troubleshooting)
> and might simplify your cabling (put USB hubs beside a bank of devices
> and run only one cable back to the server). A little bit of scripting
> with the hotplug system will let you associate the USB device using a
> given serial number with whatever name you care to give it, which
> might also simplify documentation for which router is plugged in
> where.

If you look at a modern router, eg: ASR9922, you have at least 4 serial
ports that need to be connected.  Adding a server per router gets
expensive quickly, not to include keeping the right kvm/vmware -> vm
mapping in place for the work.

> As for why they made the change... EIA-232 serial ports are becoming
> rare. Not much uses them any more and it has become hard to find a
> laptop with one built in.

Like I said, that’s why we’ve seen things like that CERN open hardware solution
come into play.  It’s cheaper than your above mentioned server and has more
robust support for the “industry standard” RJ45 pinout.

- Jared

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