I recently was running into issues with Vagrant where I’d start the virtual machine using the ‘vagrant up’ command, but I’d receive an error when trying to use vagrant ssh.

$ vagrant ssh
ssh_exchange_identification: Connection closed by remote host

I’m using a Vagrant/Ansible configuration based on roots/trellis.

I tried to look into the issue further by running the command with verbose output.

vagrant ssh -- -vvv

I noticed that it’s trying to use 127.0.0.1 to SSH into the VM on port 2222. When I try to SSH manually using ssh vagrant@192.168.50.5 -p 2222 it works fine, but with 127.0.0.1 I get the error still. It seemed that connecting to the VM from 127.0.0.1 is triggering some sort of block.

I tried to check /var/log/syslog and /var/log/auth.log (with SSHD configured for verbose mode). I don’t see any log for the failed attempt in the auth.log, though I do see a normal login. It doesn’t seem like the connection is being blocked.

I reported this issue to the roots/trellis project - #348

After further investigation I realized that I was configuring sshd on the virtual machine to use port 2222, when really Vagrant or Virtualbox was responsible for forwarding port 2222 on localhost to port 22 of the VM. I was essentially making the port forwarding that it configures invalid by changing SSHD to listen on port 2222.