#Ubuntu systems
apt-get install libpam-google-authenticator
#CentOS and Red Hat Enterprise Linux
yum install google-authenticator

auth required pam_google_authenticator.so

UsePAM yes
ChallengeResponseAuthentication yes

mkdir .ssh
chcon -t ssh_home_t -R .ssh
ls -Zd .ssh/

auth required pam_google_authenticator.so secret=/home/${USER}/.ssh/.g

AuthenticationMethods publickey, keyboard-interactive

auth required pam_unix.so

@include common-auth

auth [success=done default=ignore] pam_access.so   accessfile=/etc/security/localnet.conf

+ : ALL : 192.168.1.0/24
+ : ALL : LOCAL
- : ALL : ALL