Regardons le début du fichier sshd_config :
head /etc/ssh/sshd_config
Port 9876
Port 1234
# Supported HostKey algorithms by order of preference.
HostKey /etc/ssh/ssh_host_ecdsa_key
On cherche les doublons :
awk 'NF && $1!~/^(#|HostKey)/{print $1}' /etc/ssh/sshd_config | sort | uniq -c | grep -v ' 1 '
2 Port
Il y a bien 2x la variable Port !
Source : https://github.com/pumbaa666/How-To-Secure-A-Linux-Server#secure-etcsshsshd_config