我的 ubuntu 浏览这个正常无法访问任何站点，apt-get update甚至upgrade出现如下所示的错误，这可能是什么？
sudo apt-get update
Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [94,5 kB]
Hit:2 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu xenial InRelease
Err:3 http://br.archive.ubuntu.com/ubuntu xenial InRelease
Cannot initiate the connection to br.archive.ubuntu.com:80 (2801:82:80ff:8000::5). - connect (101: Network is unreachable) [IP: 2801:82:80ff:8000::5 80]
Err:4 http://br.archive.ubuntu.com/ubuntu xenial-updates InRelease
Cannot initiate the connection to br.archive.ubuntu.com:80 (2801:82:80ff:8000::5). - connect (101: Network is unreachable) [IP: 2801:82:80ff:8000::5 80]
Err:5 http://br.archive.ubuntu.com/ubuntu xenial-backports InRelease
Cannot initiate the connection to br.archive.ubuntu.com:80 (2801:82:80ff:8000::5). - connect (101: Network is unreachable) [IP: 2801:82:80ff:8000::5 …我开始Update information is outdated警觉了。我试过sudo apt-get update并得到这些错误：
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/raring-security/Release.gpg Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1562::13). - connect (101: Network is unreachable) [IP: 2001:67c:1562::13 80]
W: Failed to fetch http://repository.spotify.com/dists/stable/Release.gpg Something wicked happened resolving 'repository.spotify.com:http' (-11 - System error)
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/raring-security/main/i18n/Translation-en_IN Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1562::13). - connect (101: Network is unreachable) [IP: 2001:67c:1562::13 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/raring-security/main/i18n/Translation-en Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1562::13). - connect …