Host *.internal.local
    ProxyCommand bash -c 'timeout 3 nc -z %h %p || ssh -W %h:%p jump.internal.example.com'

Host *
    ProxyCommand bash -c 'timeout 3 nc -z %h %p || ssh -W %h:%p jump.external.example.com'

Host 192.168.0.*
    ProxyCommand bash -c 'timeout 3 nc -z %h %p || ssh -W %h:%p jump1.example.com'

Host 172.16.*.*
    ProxyCommand bash -c 'timeout 3 nc -z %h %p || ssh -W %h:%p jump2.example.com'

Host *
    ProxyCommand bash -c 'timeout 3 nc -z %h %p || ssh -W %h:%p fallback.jump.example.com'