A virtual serial port is an emulated serial communication interface within a virtual machine. It allows the VM to communicate with the host machine or other VMs as if it were a physical serial port. This can be useful for various purposes, including:

Older GNS3 topologies frequently show this message. GNS3’s integration of Dynamips means that if you add a router but forget to connect the Serial interface via the "Link" tool, you will see this message on boot.

Make sure: