On Feb 2, 2016, at 3:56 PM, William Herrin <bill@herrin.us> wrote:
On Tue, Feb 2, 2016 at 9:11 AM, Jared Mauch <jared@puck.nether.net> 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?
Yes. 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