1. Introduction : Want to access a Web site to obtain the corresponding HTTP service, you must first learn its corresponding IP address
And we usually accessed using a domain name, the number of network commands, nklookup can query the correspondence between the domain name -IP / IP- domain name
2.nslookup function
Mainly used for DNS name resolution, network failure when you can use this command to see if a DNS error
3. DNS
1) DNS Background
OSI reference model network layer protocol -IP primary communication protocol of the third terminal node for implementing
Because IP is a string consisting of a sequence of numbers, such as 192.168.6.12, it is not easy to remember, so that instead of the domain name;
As your network grows, managing IP- host name has become complex, with the DNS system for correspondence between the domain name to help manage IP-
2) DNS hierarchy
Domains such as: www.baidu.com is the name of a hierarchical structure, a tree structure can be implemented with the same name within the same organization; only one root structure, its child nodes are TLD
For example: xx cell 11 111 ---> xx.eleven.e xx cell 12 111 ---> xx.twelve.e although both belong to the same cell, but does not belong to the same building, the same name can be
3) domain name server (host and corresponding software management domain name)
In the hierarchy, each layer has a domain name server, and each server contains the layer below a layer of the IP addresses of all domain name servers; that is, if starting from the root domain name server to look, you can find access any domain name server
If a domain name server error, an error in the DNS resolution for the domain name, nslookup troubleshoot DNS resolution failure is also for this reason
4) DNS query mechanism
DNS queries are generally two ways: recursive queries iterative queries, here we introduce iterative query
Iterative query: the query domain name corresponding to the IP, to send a message to the local DNS name server, if the find is returned to the DNS client, if not a direct response by the local DNS server would ask the root name servers,
Then given a top-level domain root domain IP, go to access the server, the server will give IP next level server, so we continue to cycle until there is a domain name server to resolve the domain returns the corresponding IP
(There are a host cache for every query, there will always look on the host, not to visit the local domain name server query, if the local server did not save, then start iterative query)
3. nslookup common usage
The default DNS name server is the local name server can use the ipconfig / all command to view the DNS server
Non-authoritative answer: that is not to find the actual storage from the correspondence between the domain name -IP is returned from the lookup information stored in the company baidu
4. nklookup and ping
nslookup lesson for a complete IP address group, and ping just chose one connection, and does not return information on the DNS server;