我刚刚在 VirtualBox 中全新安装了 Fedora 20 作为虚拟机。我将虚拟机设置为使用 NAT 作为 VirtualBox 网络配置的一部分。
一开始我可以 ping google.com，但无法使用 Firefox 浏览。当我尝试执行时，yum update出现了以下错误：
Loaded plugins: langpacks, refresh-packagekit
Error: Cannot retrieve metalink for repository: fedora/20/x86_64. Please verify its path and try again
然后我在网络设置中禁用了 IPv6，并在 Firefox 中禁用了此选项。结果我能够使用 Firefox 进行浏览，但执行时仍然不断收到错误yum update。
当我这样做时，URLGRABBER_DEBUG=1 yum check-update我得到：
2013-12-20 11:33:35,612 attempt 1/10: https://mirrors.fedoraproject.org/metalink?repo=fedora-20&arch=x86_64
2013-12-20 11:33:35,612 opening local file "/var/cache/yum/x86_64/20/fedora/metalink.xml.tmp" with mode wb
* Adding handle: conn: 0x1c896d0
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 9 (0x1c896d0) send_pipe: 1, recv_pipe: 0
* Could not resolve host: mirrors.fedoraproject.org
* Closing connection 9
2013-12-20 11:33:45,169 exception: [Errno 14] curl#6 - "Could not resolve host: mirrors.fedoraproject.org"
2013-12-20 11:33:45,169 retrycode (14) not in list [-1, 2, 4, 5, 6, 7], re-raising
Error: Cannot retrieve metalink for repository: fedora/20/x86_64. Please verify its path and try again
但当我这样做时，ping mirrors.fedoraproject.org我得到：
ping mirrors.fedoraproject.org
PING wildcard.fedoraproject.org (209.132.181.16) 56(84) bytes of data.
64 bytes from wildcard.fedoraproject.org (209.132.181.16): icmp_seq=1 ttl=63 time=104 ms
64 bytes from wildcard.fedoraproject.org (209.132.181.16): icmp_seq=2 ttl=63 time=115 ms
64 bytes from wildcard.fedoraproject.org (209.132.181.16): icmp_seq=3 ttl=63 time=135 ms
其结果nslookup mirrors.fedoraproject.org是：
Server: 192.168.0.1
Address: 192.168.0.1#53
Non-authoritative answer:
mirrors.fedoraproject.org canonical name = wildcard.fedoraproject.org.
Name: wildcard.fedoraproject.org
Address: 209.132.181.16
Name: wildcard.fedoraproject.org
Address: 67.203.2.67
Name: wildcard.fedoraproject.org
Address: 213.175.193.206
Name: wildcard.fedoraproject.org
Address: 140.211.169.197
Name: wildcard.fedoraproject.org
Address: 152.19.134.146
Name: wildcard.fedoraproject.org
Address: 80.239.156.215
Name: wildcard.fedoraproject.org
Address: 66.35.62.166
Name: wildcard.fedoraproject.org
Address: 66.135.62.201
Name: wildcard.fedoraproject.org
Address: 85.236.55.6
我尝试在 VirtualBox 中使用桥接适配器选项，但遇到了同样的错误。
我按照建议在 NAT 模式下启用 DNS 代理，但同样的问题仍然存在（我仍然可以在 Firefox 中浏览，但 yum 无法解析主机 mirrors.fedoraproject.org）。现在命令ifconfig显示以下内容：
p2p1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.2.15 netmask 255.255.255.0 broadcast 0.0.0.0
inet6 fe80::a00:27ff:fea4:a4c6 prefixlen 64 scopeid 0x20<link>
ether 08:00:27:a4:a4:c6 txqueuelen 1000 (Ethernet)
RX packets 723 bytes 695639 (679.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 628 bytes 77437 (75.6 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 19 base 0xd020
显示cat /etc/resolv.conf如下：
nameserver 10.0.2.3
最后，我尝试了“在 NAT 模式下使用主机的解析器作为 DNS 代理”，问题终于解决了。