ssh ipv4 only

Disable ipv6 on ssh

I don’t like ipv6, so I disable the service stacks that use ipv6 (I do not disable ipv6 though because that will cause other problems)

Verify IPv6 Services

ubuntu@perfectvacationpackages:~$ netstat -plunt
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      -
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      -
tcp6       0      0 :::22                   :::*                    LISTEN      -

SSHD settings

Modify this to file to disable ssh over ipv6:

sudo vim /etc/ssh/sshd_config
ListenAddress 0.0.0.0
sudo service ssh restart

Verify IPv6 Services again

ubuntu@perfectvacationpackages:~$ netstat -plunt
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      -
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      -