ProxyCommand

What we saw in our debug message was SSH translating the fairly simple ProxyJump entry into a ProxyCommand line.

ProxyCommand is the more traditional way of setting up this kind of forwarding, but not only is it syntactically more irritating, it's also messy.

Consider the following example:

Host *
 Port 22

Host CentOS2-V4
 Hostname 192.168.33.11
 User vagrant

Host CentOS3-V4
 Hostname 192.168.33.12
 User vagrant
 ProxyCommand ssh -v -W %h:%p CentOS2-V4

Looks more awkward, doesn't it? But it works in the same way.

This can be useful on older distributions, which maybe haven't received the ProxyJump feature yet.