I'm running xenial. After I saw your comment I tried it on zesty and have yet to run into this bug on zesty. I haven't tried in the same environment yet though, I can try that later this week as well as get an apport-collect done.
As you can see below, the last login reports an ipv6 address. I verified it is using ipv6 using iftop as well. I also tried your trivial case and the same thing happened. We are running freeipa, I don't know if that would have an effect or not. If it's fixed in zesty, is there any way to get the same fix into xenial? bryceml@ratpoison:~$ ssh -4 sake Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.4.0-75-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage 0 packages can be updated. 0 updates are security updates. Last login: Tue May 2 08:50:11 2017 from 2620:10f:3007:a068:1a66:daff:fe1f:a85 bryceml@sake:~$ logout Connection to sake closed. bryceml@ratpoison:~$ ssh -4 sake Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.4.0-75-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage 0 packages can be updated. 0 updates are security updates. Last login: Tue May 2 08:50:27 2017 from 2620:10f:3007:a068:1a66:daff:fe1f:a85 bryceml@sake:~$ host sake sake.cs.byu.edu has address 192.168.168.107 sake.cs.byu.edu has IPv6 address 2620:10f:3007:a068:1a66:daff:fe1f:d96f bryceml@sake:~$ bryceml@ratpoison:~$ ssh -4 ip6-localhost The authenticity of host 'ip6-localhost (<no hostip for proxy command>)' can't be established. ECDSA key fingerprint is SHA256:nhU3sXqrZoF3zNUxlWAfuLebsMSFhRuycFFWHlL2RRY. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'ip6-localhost' (ECDSA) to the list of known hosts. Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.4.0-75-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage 0 packages can be updated. 0 updates are security updates. Last login: Tue May 2 08:43:46 2017 from 2620:10f:3007:a080:1a66:daff:fe1f:1057 bryceml@ratpoison:~$ logout Connection to ip6-localhost closed. bryceml@ratpoison:~$ ssh -4 ip6-localhost Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.4.0-75-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage 0 packages can be updated. 0 updates are security updates. Last login: Tue May 2 08:57:16 2017 from ::1 bryceml@ratpoison:~$ -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1687482 Title: -4 flag doesn't work Status in openssh package in Ubuntu: Incomplete Bug description: Whenever I use the -4 flag on ssh, it still uses the ipv6 address from dns instead of forcing ipv4 like it says it is supposed to do in the man page. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1687482/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
