Enable telnet access in ASAV
To work with ASAv firewall through telnet, we need serial port to be enabled. Unfortunately, ASAv firewall serial port is disabled by default. However, we still can manually enable it. We need to create a file on the root of Disk0: called use_ttyS0 to enable the serial interface. The easiest way to accomplish this is to clone the existing \coredumpinfo\coredump.cfg file and rename it. To clone it, use the following commands. That S0 is capital letter S and number zero 0 not S and the letter O. Verify that the file is cloned successfully with the command dir.
ciscoasa#cd coredumpinfo
ciscoasa#copy coredump.cfg disk0:/use_ttyS0
Now you can shutdown your ASAv firewall and change the console type from "vnc" to "telnet" instead by right click ASAv, and select configure. We don't need to save the configuration of ASAv firewall virtual servers at this point.
Power on your ASAv firewall back, right click on it and choose console to open the access