Fedora 20: "호스트를 확인할 수 없습니다: download.fedoraproject.org"

Fedora 20을 새로 설치했는데 인터넷 연결(핑, 웹 브라우저)이 제대로 작동하고 있습니다. 그러나 시도하면 yum update다음과 같은 오류 메시지가 나타납니다.

failure: repodata/repomd.xml from download.fedoraproject.org_pub_fedora_linux_updates_testing_20_i386_: [Errno 256] No more mirrors to try.
http://download.fedoraproject.org/pub/fedora/linux/updates/testing/20/i386/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: download.fedoraproject.org"

추가 정보:

$ cat /etc/issue
Fedora release 20 (Heisenbug)
Kernel \r on an \m (\l)

$ ls /etc/yum.repos.d/
download.fedoraproject.org_pub_fedora_linux_updates_testing_20_i386_.repo
fedora.repo
fedora-updates.repo
fedora-updates-testing.repo
fedora-updates-testing.repo~
rpmfusion-free-rawhide.repo
rpmfusion-free.repo
rpmfusion-free-updates.repo
rpmfusion-free-updates-testing.repo
rpmfusion-nonfree-rawhide.repo
rpmfusion-nonfree.repo
rpmfusion-nonfree-updates.repo
rpmfusion-nonfree-updates-testing.repo

나는 또한 다음을 시도했습니다(도움이 될 수도 있습니다).

# yum-config-manager --disable rpmfusion-free-source
Loaded plugins: langpacks
=============================== repo: rpmfusion-free-source ===============================
[rpmfusion-free-source]
async = True
bandwidth = 0
base_persistdir = /var/lib/yum/repos/x86_64/20
baseurl = 
cache = 0
cachedir = /var/cache/yum/x86_64/20/rpmfusion-free-source
check_config_file_age = True
cost = 1000
deltarpm_metadata_percentage = 100
deltarpm_percentage = 
enabled = False
enablegroups = True
exclude = 
failovermethod = priority
gpgcadir = /var/lib/yum/repos/x86_64/20/rpmfusion-free-source/gpgcadir
gpgcakey = 
gpgcheck = True
gpgdir = /var/lib/yum/repos/x86_64/20/rpmfusion-free-source/gpgdir
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-rpmfusion-free-fedora-20
hdrdir = /var/cache/yum/x86_64/20/rpmfusion-free-source/headers
http_caching = all
includepkgs = 
ip_resolve = 
keepalive = True
keepcache = False
mddownloadpolicy = sqlite
mdpolicy = group:small
mediaid = 
metadata_expire = 604800
metadata_expire_filter = read-only:present
metalink = 
minrate = 0
mirrorlist = http://mirrors.rpmfusion.org/mirrorlist?repo=free-fedora-source-20&arch=x86_64
mirrorlist_expire = 86400
name = RPM Fusion for Fedora 20 - Free - Source
old_base_cache_dir = 
password = 
persistdir = /var/lib/yum/repos/x86_64/20/rpmfusion-free-source
pkgdir = /var/cache/yum/x86_64/20/rpmfusion-free-source/packages
proxy = False
proxy_dict = 
proxy_password = 
proxy_username = 
repo_gpgcheck = False
retries = 10
skip_if_unavailable = False
ssl_check_cert_permissions = True
sslcacert = 
sslclientcert = 
sslclientkey = 
sslverify = True
throttle = 0
timeout = 30.0
ui_id = rpmfusion-free-source/20/x86_64
ui_repoid_vars = releasever,
   basearch
username = 

이 문제를 어떻게 해결할 수 있나요?