Using Google Public DNS

转自：http://code.google.com/speed/public-dns/docs/using.html
谷歌的公共dns



Configuring your network settings to use Google Public DNS
When you use Google Public DNS, you are changing your DNS "switchboard" operator from your ISP to Google Public DNS.
In most cases, the IP addresses used by your ISP's domain name servers are automatically set by your ISP via the Dynamic Host Configuration Protocol (DHCP). To use Google Public DNS, you need to explicitly change the DNS settings in your operating system or device to use the Google Public DNS IP addresses. The procedure for changing your DNS settings varies according to operating system and version (Windows, Mac or Linux) or the device (computer, phone, or router). We give general procedures here that might not apply for your OS or device; please consult your vendor documentation for authoritative information.
Note: We recommend that only users who are proficient with configuring operating system settings make these changes.
Important: Before you start
Before you change your DNS settings to use Google Public DNS, be sure to write down the current server addresses or settings on a piece of paper. It is very important that you keep these numbers for backup purposes, in case you need to revert to them at any time.
After changing your settings, if you encounter a problem and cannot connect to the Internet, please call our support numbers for troubleshooting instructions.
We also recommend that you download this page and print it, in the event that you encounter a problem and need to refer to these instructions.
Google Public DNS telephone support
877-590-4367 in the U.S.
770-200-1201 outside the U.S.
Google Public DNS IP addresses
The Google Public DNS IP addresses are as follows:
8.8.8.8
8.8.4.4
You can use either number as your primary or secondary DNS server. You can specify both numbers, but do not specify one number as both primary and secondary.