一般情況下，網(wǎng)絡(luò)提供商會(huì)通過(guò)主干網(wǎng)路由的DHCP功能，在用戶接入互聯(lián)網(wǎng)時(shí)自動(dòng)分配主要DNS和次要DNS（DNS是啥，請(qǐng)自己百度哦）. 但是而這些經(jīng)過(guò)嚴(yán)格管控的DNS服務(wù)器由于偉大的長(zhǎng)城服務(wù)的緣故，會(huì)將某些網(wǎng)站的真實(shí)IP解析到一個(gè)錯(cuò)誤或者不存在的IP地址上（此稱(chēng)之為DNS投毒），所以你常常會(huì)發(fā)現(xiàn)，前兩天還能上去的站點(diǎn)，今天卻提示無(wú)法找到站點(diǎn)~，怎么辦？換上下邊列表中的DNS，問(wèn)題可以得到很大程度上的緩解（不能說(shuō)百分百解決問(wèn)題）；另外，有時(shí)候當(dāng)網(wǎng)絡(luò)擁堵時(shí)換上這些dns，會(huì)自動(dòng)查詢非常規(guī)線路上的主機(jī)IP（很多站點(diǎn)的主機(jī)都是云分布的，它們自動(dòng)提供您最合適的線路，例如，換上google的dns后，多數(shù)智能站點(diǎn)會(huì)自動(dòng)解析到美國(guó)的主機(jī)上，而這個(gè)站點(diǎn)可能在中國(guó)，英國(guó)等其他國(guó)家也有服務(wù)器）；最后，有時(shí)候ISP的dns也會(huì)受到攻擊等因素而夯機(jī)~，這時(shí)候就是下邊這dns派上用場(chǎng)的時(shí)候了。

這些DNS都是符合安全級(jí)別的，基本都能過(guò)濾成人站點(diǎn)、僵尸網(wǎng)絡(luò)和釣魚(yú)站點(diǎn)，可以用來(lái)抵御色情信息為對(duì)未成年人的侵害，如果你需要成人類(lèi)DNS服務(wù)，請(qǐng)自尋收費(fèi)的DNS服務(wù)器~

列表摘自about站點(diǎn)。

免費(fèi) & 公眾 DNS 服務(wù)器列表 (2013年十月更新)

[1] The DNS servers listed above as Level3 will automatically route to the nearest DNS server operated by Level3 Communications, the company that provides most of the ISPs in the US their access to the Internet backbone.

[2] Google 同時(shí)提供基于 IPv6 的公開(kāi) DNS 服務(wù): 【2001:4860:4860::8888 and 2001:4860:4860::8844】.

[3] Securly's DNS servers block adult content by default, including of course X-rated content but also adult oriented pages on websites like Wikipedia, adult themed searches on Google, and more. The grown-ups in the house can sign up here to bypass all restrictions.

[4] OpenDNS also offers DNS servers that block adult content, called OpenDNS FamilyShield. It's also free but you do have to sign up here. A premium DNS offering is also available, called OpenDNS Home VIP.

[5] The Norton ConnectSafe DNS servers listed above block sites hosting malware, phishing schemes, and scams. Use 198.153.192.50 and 198.153.194.50 to block those sites plus those with pornographic content. Use 198.153.192.60 and 198.153.194.60 to block all previously mentioned site categories plus those Norton deems "non-family friendly."

[6] GreenTeamDNS "blocks 18 categories which include malware, botnets, dangerous websites, adult related content, aggressive/violent sites as well as advertisements and drug-related websites" according to their FAQ page. Premium accounts have more control.

[7] Register here with SafeDNS for content filtering options in several areas.

[8] The DNS servers listed here for OpenNIC are just two of many in the US and across the globe. Instead of using the OpenNIC DNS servers listed above, see their complete list of public DNS servers here and use two that are close to you or let them tell you that automatically here. OpenNIC also offers some IPv6 public DNS servers.

[9] These Public-Root DNS servers are the only two currently operating in the United States but if you're located ouside the US, see their complete list here and choose the best servers based on your location.

[10] The DNS servers are uncensored, operated by a privately funded individual, and are physically located in Denmark. You can read more about them here. IPv6 DNS servers are also available at 2002:d596:2a92:1:71:53:: and 2002:5968:c28e::53

[11] Hurricane Electric also has an IPv6 public DNS server available: 2001:470:20::2.

[12] puntCAT is physically located near Barcelona, Spain. The IPv6 version of their DNS server is 2a00:1508:0:4::9.

Note: Primary DNS servers are sometimes called preferred DNS servers and secondary DNS servers are sometimes called alternate DNS servers. Primary and secondary DNS servers can be "mixed and matched" to provide another layer of redundancy.