DNS Server Notes

1. Domain name resolution: domain name-->DNS server-->IP address;

2. DNS domain name is also called the DNS namespace, it is managed by hierarchical tree structure;

3. DNS Domain name structure: root domain--top level domain name (domain name), level two domain name, level three domain name .....

4. top-level domain is generally divided into general and national two categories, for the two-level domain name, the provisions are divided into categories of domain names and administrative domain names;

5. in the absence of DNS, through a Hosts file on the computer (/etc/hosts) to implement the host name to IP address resolution, by manually adding paired host name and IP address to the Hosts file, the system through automatic query method to achieve resolution,

6. DNS The server does not rely on a large mapping file, it uses a distributed structure to manage the domain name, so that each host only needs to set the IP address of the DNS server to use, and each DNS server only need to maintain the DNS records in its domain. The DNS servers distributed in different domains constitute the distributed domain name database system.

7. DNS the process of resolving a domain name:

(1) the host system issues a DNS resolution request to the local DNS server,

(2) after the local DNS server receives the request, first in its own DNS database to find the matching domain name and IP address corresponding records, if found, directly back to the client and end the DNS resolution process; Conversely, the request is forwarded to the root domain DNS server;

(3) The root domain DNS server finds the top-level domain for the domain name, then the top-level domain to the level two domain, and so on, until finally the domain name and IP address that need to be resolved are found, and the result is returned to the local DNS server;

(4) The final local DNS server returns the results to the client and ends the parsing process;

(5) If the final lookup is not found, the local DNS server sends an unresolved error message to the client;

8. The forward parsing zone file is used to map the domain name and IP address, and the reverse resolution zone file is used to define the resolution of the IP address to the domain name, which takes the same options and formats as the forward parsing zone file, but because of the reverse parsing, the file is recorded using PTR pointers, not the host record;

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DNS Server Notes