Why apt-get update fail to connecting to dl.google.com?

Disable_ipv6_ubuntu

When I have this problem, I disable IPv6 in Ubuntu and that fix the problem, in order to do that, please follow these steps:

To disable IPv6, you have to open /etc/sysctl.conf using any text editor and add the following lines at the end:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
If IPv6 is still enabled, then the problem is that sysctl.conf is still not activated.

In that case, open a terminal(Ctrl+Alt+T) and type the command:

sudo sysctl -p
The output will be very similar to these 3 lines:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
After that, execute:

$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6
If you see 1 in the output, then IPv6 has been successfully disabled.

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https://askubuntu.com/questions/991438/why-apt-get-update-fail-to-connecting-to-dl-google-com