Description of problem: Mirrors not available on update fedora 26 by dnf. Version-Release number of selected component (if applicable): 26 Error is like: Error: Error downloading packages: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metalink?repo=updates-released-f26&arch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]
This cannot be fixed in DNF, it looks like you have problems with your network, namely DNS.
*** Bug 1475822 has been marked as a duplicate of this bug. ***