Use Opendns to Cross the Great Firewall in China
once upon a time
- we can log in facebook and google directly
- but nowadays we can not
- and because DNS hijacking and DNS cache posioning, we can not log in directly anymore
what is DNS hikacking?
- DNS hijacking(劫持)
- to simplifiy the idea
- when you type in google.com, you will not attach the google.com
- you will be direct to the baidu.com
- and this is the DNS hijacking
- and the reason why this will happen is that the DNS server is cracked and the domain name will be parse to the wrong ip.
- and recently the govenment is using this kind of strategy
what is DNS cache posioning?
- this idea used to be used to block the youtube, facebook website
- this is on the protocol layer
- and the mechisim is that when you want to launch the particular website
- the port 53 UDP is check and when they found that you want to attach particular website, they will change the domain name parse DNS server into a wrong one and then you will not be able to get the correct ip.
- then you will not be able to get to the website.
How dns works?
- first, when we use some domain name like “www.facebook.com”
- and when we type the domain name into the website
- the website will send the name to the dns server to check the ip
- then return the ip the our computer
- then we will know the ip of the target website
- and we will be able to get to the website
why can we use this in China?
- Because in China when you type “www.google.com”
- they block the dns parse not the connection
- so we will be able to break through the wall if we use the other dns server to help use parse the domain name
how to use opendns
- change the dns settings in the PC or laptop
- if you want to use the google dns
- set “188.8.131.52” and “184.108.40.206”
- if you want to use the opendns
- set “220.127.116.11” and “18.104.22.168”
- or set “22.214.171.124” and “126.96.36.199”
- then if you are using Max 10.8 or above
- you can renew the dns setting using
- “sudo killall -HUP mDNSResponder”
when not to use opendns
- when you are using the payment or something private