vagrant upでエラーが生じたときの対処法

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.

timeout during server version negotiating


vb.customize ['modifyvm', :id, "--natdnshostresolver1", "on"]
vb.customize ['modifyvm', :id, "--natdnshostresolver1", "off"]