SSH ProxyCommand errors

Question

I'm trying to understand why SSH proxycommand isn't working. I have a SSH config file in a custom location as below.

vagrant@ansible:~$ cat ~/.ssh/cml-config
Host mgmt-lxc
  HostName 10.17.238.146
  IdentityFile ~/.ssh/id_rsa
  User Rod

Host 10.255.0.*
  ProxyCommand ssh -W %h:%p mgmt-lxc
vagrant@ansible:~$

I can SSH to the jumphost and from there to another device.

vagrant@ansible:~$ ssh -F ~/.ssh/cml-config mgmt-lxc
Rod@mgmt-8Fe5bN$ ssh [email protected]
Warning: Permanently added '10.255.0.47' (RSA) to the list of known hosts.

            ,,,,,
            /'''\
           ( o o )
      -oOOO--(_)--OOOo-------------------------------------------
       Router: Core-1
                      Secured system for authorized users only.
       .oooO          Unauthorized access is strictly prohibited.
        (   )   Oooo. All activities may be logged and monitored.
      ---\ (----(   )--------------------------------------------
          \_)    ) /
                (_/
Password:

However when I attempt to SSH directly to 10.255.0.47 using the custom SSH key I get an error.

vagrant@ansible:~$ ssh -F ~/.ssh/cml-config [email protected]
ssh: Could not resolve hostname mgmt-lxc: Name or service not known
ssh_exchange_identification: Connection closed by remote host
vagrant@ansible:~$

I'm running Ubuntu Xenial64.

Answer 1

Add -F /the/path/to/.ssh/cml-config in your ssh -W command used as ProxyCommand (I am not sure the ~ path will work here, so try it and maybe use the full path).

Because otherwise your ssh interactive command will run ssh -W ... mgmt-lxc but then it will have no configuration file to read to discover that mgmt-lxc is not a true name resolving but a nickname you used in your configuration file.

Or add mgmt-lxc in /etc/hosts or equivalent with its IPv4 address 10.17.238.146.

Or put everything in .ssh/config instead, as it is the default and will simplify your usage.