Talk:DNS

From S23Wiki
Jump to: navigation, search

Problem:
Sometimes the DNS that a network uses to access the net will go down..so there is access to the Internet but one cannot browse it since domain names aren't resolving to IP's.

Question:
Lets say one does not have access to fix the DNS, How does one use tools like nslookup to manually by-pass DNS resolution, or any other tool? So essentially how can you still browse the net and not be detoured by no DNS resolution?

Answer:

oki first a few points,

  • DNS converts then Domain name to IP address. (ie wiki.s23.org -> 217.20.122.189)
  • DNS connects to a "server" to get this information.
  • If your DNS is down you will need to do "DNS lookup" using another DNS server, HINT, you will need to know the IP address of this server rather then the Name of it (because your DNS is down).
  • There are "public access DNS servers" google:"public DNS servers", one of the results was -> [soa.granitecanyon.com] which will give you a dns server IP of 205.166.226.38.


with all the above in mind...

do a nslookup like nslookup [computer-to-find] [server]

'nslookup wiki.s23.org 205.166.226.38'

which should return something like...

Non-authoritative answer:
Name:    wiki.s23.org
Address:  213.61.105.210

then use that IPaddress in your browser...

But i here you say this did not work i see no lovely wiki???

that's because wiki.s23.org is redirected to another domain using magic, what do you do now then???

well i know that the s23 wiki is hosted on is-root.de so i did a nsloopup on that...

Non-authoritative answer:
Name:    is-root.de
Address:  217.20.118.146

so into my browser goes '217.20.118.146', and joy of joys i see a web page, but oh no this is no good at all, as its just showing the index page and not the wiki... come get smart the wiki was always in ir-root.de/wiki, so guess what you need to point to http://217.20.118.146/wiki/, and ta dar... magic its working.

OK so this seems rather complicated, and it will be but at least if you have an example to learn from you have more of a chance.


also you could try manually setting your DNS to the IP of the public server...

do this from [Control Panel] --> [Network and Dial-up Connections] --> [Local Area Connection] --> [Internet Protocol (TCP/IP)] --> [Properties] --> [Use the Following DNS server address] =)

Some popular IPs for DNS-less people

s23.org                 A       217.20.122.189
is-root.de              A       217.20.118.146
dronf.de                A       217.20.122.188

google.com              A       216.239.57.99
google.com              A       216.239.39.99

and here it gets more interesting,when there is not a single machine behind it:

mutante@zyme:~  host en.wikipedia.org

en.wikipedia.org        CNAME   rr.wikimedia.org
rr.wikimedia.org        CNAME   rr.knams.wikimedia.org
rr.knams.wikimedia.org  A       145.97.39.134
rr.knams.wikimedia.org  A       145.97.39.135
rr.knams.wikimedia.org  A       145.97.39.136
rr.knams.wikimedia.org  A       145.97.39.137
rr.knams.wikimedia.org  A       145.97.39.138
rr.knams.wikimedia.org  A       145.97.39.139
rr.knams.wikimedia.org  A       145.97.39.131
rr.knams.wikimedia.org  A       145.97.39.133

("host" is a command to lookup hostnames under Linux.)


Related Debian packages:

dns-browse - Front-ends to DNS search

host - utility for querying DNS servers

no-ip (DynDNS client)


More info on the nslookup command

Windows Help nslookup

Nslookup This diagnostic tool displays information from Domain Name System (DNS) name servers. Before using this tool, you should be familiar with how DNS works. Nslookup is available only if the TCP/IP protocol has been installed.

Modes

Nslookup has two modes: interactive and noninteractive.

If you need to look up only a single piece of data, use noninteractive mode. For the first argument, type the name or IP address of the computer to be looked up. For the second argument, type the name or IP address of a DNS name server. If you omit the second argument, the default DNS name server is used.

If you need to look up more than one piece of data, you can use interactive mode. Type a hyphen (-) for the first argument and the name or IP address of a DNS name server for the second argument. Or, omit both arguments and the default DNS name server is used.

nslookup [-option ...] [computer-to-find | - [server]]

Parameters

-option ...

Specifies one or more nslookup commands as a command-line option. For a list of commands, see Nslookup Subcommands. Each option consists of a hyphen (-) followed immediately by the command name and, in some cases, an equal sign (=) and then a value. For example, to change the default query type to host (computer) information and the initial time-out to 10 seconds, you would type:

nslookup -querytype=hinfo -timeout=10

The command line length must be less than 256 characters.

computer-to-find

Looks up information for computer-to-find using the current default server or using server if specified. If computer-to-find is an IP address and the query type is A or PTR, the name of the computer is returned. If computer-to-find is a name and does not have a trailing period, the default DNS domain name is appended to the name. This behavior depends on the state of the set options: domains, srchlist, defname, and search.

To look up a computer not in the current DNS domain, append a period to the name.

If you type a hyphen (-) instead of computer-to-find, the command prompt changes to nslookup interactive mode.

server

Specifies to use this server as the DNS name server. If you omit server, the default DNS name server is used.