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 Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1687482 Title: -4 flag doesn't work To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1687482/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
