我剛剛在 VirtualBox 中全新安裝了 Fedora 20 作為虛擬機器。我將虛擬機器設定為使用 NAT 作為 VirtualBox 中網路配置的一部分。
起初我可以 ping 通 google.com，但無法使用 Firefox 瀏覽。當我嘗試執行時yum update出現以下錯誤：
Loaded plugins: langpacks, refresh-packagekit
Error: Cannot retrieve metalink for repository: fedora/20/x86_64. Please verify its path and try again
然後我在網路設定中停用了 IPv6，並且在 Firefox 中也停用了該選項。結果我可以使用 Firefox 瀏覽，但在執行yum update.
當我這樣做時，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
但是當我這樣做時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
的結果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
我嘗試在 VirtualBox 中使用橋接適配器選項，但遇到了相同的錯誤。
我遵循了在NAT模式下啟用DNS代理的建議，但同樣的問題仍然存在（我仍然可以在Firefox中瀏覽，但yum無法解析主機mirrors.fedoraproject.org）。現在ifconfig命令顯示：
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
顯示了這一點cat /etc/resolv.conf：
nameserver 10.0.2.3
最後，我嘗試了“在NAT模式下使用主機的解析器作為DNS代理”，問題終於得到解決。