Having got hold of a Cisco router I had to try to connect to it via my Windows installed in VirtualBox, problem was the COM port was not recognised in the VirtualBox settings, every time I tried to start windows it failed with an error, one of these errors suggested checking the permissions and user groups to make sure these were correct.

Turns out I needed to add my (host) user to the correct group, use the command
ls -l /dev/ttyS*
to list the current groups for tty's.

As can be seen here the serial ports are all in the dialout group so using the user manager I added myself to the dialout group. Once that was done ( remember to logout and back in once you change group associations!! ) I set up the serial port in the virtualbox settings COM1, choose the Host Device option and add /dev/ttyS0 as the path.

Once this was done I started Windows and it now booted fine and once I was logged in, Windows detected new hardware and installed it.

Now I am able to console into the router and all is good.