Seems to be able to resolve the hostnames to ip v6 address (why not ipv4?), but more is not possible, a ping seems to freeze:
Linux proxmox 4.15.17-1-pve #1 SMP PVE 4.15.17-9 (Wed, 9 May 2018 13:31:43 +0200) x86
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Thu Jun 7 07:37:06 2018
root@proxmox:~# apt-get update
Ign:1 https://enterprise.proxmox.com/debian/pve stretch InRelease
Ign:2 https://enterprise.proxmox.com/debian/pve stretch Release
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Err:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
401 Unauthorized
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
0% [Connecting to ftp.ch.debian.org (2001:67c:10ec:3dd1::42)] [Connecting to prod.debian.map.fastly^C
root@proxmox:~# ping google.com
PING google.com(zrh04s14-in-x0e.1e100.net (2a00:1450:400a:802::200e)) 56 data bytes
regards, jan
Linux proxmox 4.15.17-1-pve #1 SMP PVE 4.15.17-9 (Wed, 9 May 2018 13:31:43 +0200) x86
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Thu Jun 7 07:37:06 2018
root@proxmox:~# apt-get update
Ign:1 https://enterprise.proxmox.com/debian/pve stretch InRelease
Ign:2 https://enterprise.proxmox.com/debian/pve stretch Release
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Ign:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
Ign:3 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise all Packages
Err:4 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise amd64 Packages
401 Unauthorized
Ign:5 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en_US
Ign:6 https://enterprise.proxmox.com/debian/pve stretch/pve-enterprise Translation-en
0% [Connecting to ftp.ch.debian.org (2001:67c:10ec:3dd1::42)] [Connecting to prod.debian.map.fastly^C
root@proxmox:~# ping google.com
PING google.com(zrh04s14-in-x0e.1e100.net (2a00:1450:400a:802::200e)) 56 data bytes
regards, jan