Errors::NetSSHException: An error occurred in the underlying SSH library

[hawksbill]

Initially the error seem to point to the net-ssh library. The ssh-agent on the host, but it turned out to be none of these.

DEBUG ssh: == Net-SSH connection debug-level log END ==
INFO ssh: SSH not up: #<Vagrant::Errors::NetSSHException: An error occurred in the underlying SSH library that Vagrant uses.
The error message is shown below. In many cases, errors from this
library are caused by ssh-agent issues. Try disabling your SSH
agent or removing some keys and try again.
If the problem persists, please report a bug to the net-ssh project.

This error is quite common. When deploying vagrant VM to AWS. The ssh connection was not getting through, because the correct entry had not been added to the the AWS security group, it needed the correct CIDR ip address.

Most of the time when ssh cannot connect through to the provisioned VM, it's an incorrect firewall rule that's the issue.