Shulou(Shulou.com)06/03 Report--

The principle and configuration of DNS Service

DNS is a set of protocols and services whose basic function is to establish mapping management between hostnames and corresponding IP addresses.

* Host name is easy to remember

* A digital IP address may change for a variety of reasons, while the hostname can remain the same.

The composition of DNS

Root domain: it is "." (dot), managed by the Internet name Registration Authority, which assigns responsibility for the management of various parts of the domain name space to organizations connected to the Internet.

Top-level domain: the subordinate domain of the root domain, managed by the Internet name authority, there are two common types.

* Organization domain: use a three-character code to identify the main functions or activities of the organization contained in the DNS domain, as shown in the figure

* country or region top-level domain: a two-character country or region code

Second-level domain name: the name registered to an individual, organization, or company. For example, "google.com" is based on the top-level domain ".com". The second-level domain can include hosts and subdomains, such as "mail.google.com" and subdomains such as "news.google.com".

Hostname: at the bottom of the domain name spatial structure, combined with the preceding domain name (DNS suffix) to form a FQDN (fully qualified domain name), such as "aaa.bbb.com", where aaa is the hostname and "bbb.com" is called (DNS suffix).

FQDN is the full domain name, the full name of a system rather than its host name.

Query process of DNS

(1) the client passes the www.benet.com information to its preferred DNS server.

(2) the preferred DNS server for the DNS client checks the zone database, and since this server has no authorization record for the benet.com domain, it passes the query information to the root domain DNS server and requests the host name to be resolved.

(3) the root domain DNS server returns the IP address of the DNS server responsible for resolving the "com" top-level domain to the preferred DNS server of the DNS client.

(4) the preferred DNS server sends the request to the DNS server responsible for the "com" domain.

(5) the server responsible for the "com" domain returns the IP address of the DNS server responsible for the "benet.com" domain to the preferred DNS server upon request.

(6) the preferred DNS server sends requests to the DNS server responsible for the "benet.com" zone.

(7) because this server has a record of www.benet.com, it returns the IP address of www.benet.com to the preferred DNS server.

(8) the client's preferred DNS server sends the IP address of the www.benet.com to the client.

(9) after domain name resolution is successful, the client sends the http request to the Web server.

(10) the Web server responds to the client's access request, and the client can access the target host.

The query method of DNS:

Recursive query: the result obtained by the client can only be success or failure.

Iterative query: if a client requests data, the DNS server returns the correct address; if the DNS server does not request data, it returns a pointer.

The domain name query of DNS server can be divided into two forms according to the query content: forward query and reverse query.

Forward query is to find the IP address by the domain name.

The reverse query is to find the domain name by the IP address.

Necessary conditions for providing DNS services

1. Have a fixed IP address

two。 Install and start the DNS service

3. Have zone files, configure transponders, or configure root prompts

Case: a company has a DNS server whose internal local area network uses benet.com as its domain name. Now the company has set up a branch in Shanghai, and the Shanghai branch uses a special line to connect with the head office. The Shanghai branch plans to use "sh.benet.com" as the domain name and resolve it locally. How should it be implemented?

# Sub-domains can be established by delegation. The specific steps are as follows:

1. Add a host record on the DNS server where the parent zone is located, and the IP address of the host record is the DNS server where the child domain is located.

two。 Right-click "benet.com" and choose "New delegation" from the pop-up shortcut menu.

3. Create a new delegated domain name "sh". Next

4. Add a name server to specify the name of the DNS server that can host the delegation

5. Enter the full FQDN of the server, click resolve, and next, complete the delegation.

6. Create a new "main zone" on the DNS server in Shanghai with the name of "sh.benet.com", and complete the new zone.

The Shanghai branch can manage domain name records locally, and the head office can also access the Shanghai branch through the domain name suffix "sh.benet.com".

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