The System Administrator will often come across a situation where an SSH connection to Host B is only possible by making a detour via SHH to Host A:
client -> ssh A -> ssh B

To shorten this two-step process, an entry can be made in the ~/.ssh/config of Host A as "Jumphost", to ensure that this step is always followed in future.

Host Bdirekt
Hostname $IP_von_B
User rwo 
ProxyCommand ssh root@A.intern.lan nc %h %p

In the first row an alias is defined - this can be arbitrary, but some relation to B would make sense. The second row defines the host name of B - for permissions in every network thereafter, an IP is a good idea as a hostname! The option ProxyCommand defines the underlying Jump function - where access via SSH to A and the pipe of data occurs by means of numerical control.

Where SSH keys are properly allocated, there are no more queries. A simple ssh Bdirect leads directly to host B.

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