Virtual serial ports in Windows VM hosts (for IOS XRv)

I’ve been trying to play around with Cisco IOS XRv this morning – the virtual machine version of the IOS XR software used on the ASR-9000 and CRS-1 series routers. Having expensive hardware like that for a simple test environment is tricky, but XRv means you can have one on your desktop.

The VM boots fine, but then leaves you with a nearly-blank screen that says “Booting IOS XRv”. What happened? All the action is happening on the serial port of the device, just like on a real router. So you need a serial port in the VM, and some way to talk to that.

I went through quite a few different versions of this, using NPTP, and VMwareGateway. I tried with VirtualBox and VMware Workstation. In each case, I would get a login prompt that didn’t work. I would see my password echoed back on the screen, and the router would generally act strangely – showing a password prompt and immediately saying that login failed, for example.

Then I found out that PuTTY can talk directly to a named pipe. So all you actually need is PuTTY. Fire it up, select Serial, then paste in the named pipe name you used when configuring the VM. It works! And login works, too!

So the full process: import the OVA. Then add a serial port to the VM (if it’s in VMware Workstation, VirtualBox already has one). Set the serial port type to Named Pipe, and add something like “.\pipe\my_xrv” to the name for the pipe. It MUST start with “.\pipe\”. In VMware, you want to say “This is the server”. In VBox, you say “Create Pipe”.

Then start the VM, and use Putty to connect (with Serial connection selected) to “.\pipe\my_xrv” where it usually says “COM1”.

Obviously the same technique works for anything else that needs a serial port to talk to the world.

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