DNS of Linux services (i)

DNS and Bind

Sockets:

C:

Client: The program that initiated the application request;

Server: A program that responds to a request (providing a service);

Listen:socket

Transport Layer Protocol: TCP, UDP, SCTP

Tcp:transmission Control Protocol

Connection-oriented protocol: a virtual connection needs to be established prior to communication between two parties;

Udp:user Datagram Protocol

No connection protocol: the need to establish a virtual connection prior to the communication between the two parties;

Dns:domain Name Service, Application layer protocol

C

53/UDP, 53/tcp

Www.magedu.com:FQDN (full qualified Domain Name)

Tld:top level Domain

Organizational domain:. com,. NET,. org,. gov,. edu,. mil

Country domain:. IQ,. TW,. HK,. JP,. cn,...

DNS Query type:

Recursive query:

Iterative query:

DNS Name resolution method:

Name-to-IP: Forward parsing

IP--Name: Reverse resolution

Note: The namespace of both is not the same space, that is, not the same tree; therefore, it is not the same parse library;

Domain: magedu.com.

Www.magedu.com. 1.1.1.1

Ftp.magedu.com. 2.2.2.2

Bbs.magedu.com. 3.3.3.3

Cloud.magedu.com. 4.4.4.4

DNS Server type:

Responsible for parsing at least one domain:

Primary name server;

Auxiliary name server;

Not responsible for the analysis:

Cache name servers;

The process through which a complete query request passes:

Client--The Hosts file--DNS Local Cache---DNS Server (recursion)--

The domain in which you are responsible for parsing: Querying the database directly and returning the answer;

Not yourself. Parsing domain: Server Cache--Iteration (iteration)

Analytic answer:

Affirmative answer:

Negative answer: There is no key to the query, therefore, there is no value corresponding to its query key;

Authoritative answer: The answer returned by the directly responsible DNS server;

Non-authoritative answer:

Primary-Secondary DNS servers:

Primary DNS server: The server that maintains the domain database that is responsible for parsing, read and write operations can be carried out;

From the DNS server: From the primary DNS server or other from the DNS server "copy" a copy of the parse library, but only read operations;

How the copy operation is implemented:

Serial number: Serial, which is the version number of the database, the version number is incremented when the contents of the main server database change;

Refresh time interval: refresh, check the serial number update status from the server every time to the main server;

Retry interval: Retry the time interval to attempt the request from the server when it fails to request synchronization from the primary server;

Expiration time: Expire, when the primary server is always not contacted from the server, how long after the data is discarded from the primary server, stop providing services;

Cache duration for negative answers:

Master server "notifications" from the server to update data at any time;

Zone transfer:

Full-Volume transmission: AXFR, transmission of the entire database;

Incremental transfer: IXFR, transferring only the data of variables;

Zone (Zone) and domain:

Magedu.com Domain:

FQDN-To-IP

Forward parsing Library;

IP-To-FQDN

Reverse Parse library;

Zone database files:

Resource record: Resource record, abbreviated RR;

Records have type: A, AAAA, PTR, SOA, NS, CNAME, MX

Soa:start of authority, starting authorization record; A zone resolution library has and can have only one SOA record, and must be placed in the first article;

Ns:name service, domain name services record; A zone resolution library can have multiple NS records; One of them is the main;

A:address, address record, FQDN---IPv4;

AAAA: Address record, FQDN---IPv6;

Cname:canonical name, alias record;

Ptr:pointer,ip to FQDN

Mx:mail eXchanger, mail exchanger;

Priority: 0-99, the smaller the number, the higher the priority;

Definition format for resource records:

Syntax: Name [TTL] in Rr_type value

Soa:

Name: Names of the current region, such as "mageud.com.", or "2.3.4.in-addr.arpa." ；

Value: Multi-Part composition

(1) The zone name of the current zone (you can also use the primary DNS server name);

(2) The current regional administrator's e-mail address, but the address can not use the @ symbol, the general use of the point number to replace;

(3) (the definition of the master-slave Service Coordination attribute and the TTL of the negative answer)

For example:

magedu.com. 86400 in SOA magedu.com. Admin.magedu.com. (

2017010801; Serial

2H; Refresh

10M; Retry

1W; Expire

1D; Negative answer TTL

)

Ns:

Name: The region names of the current zone

Value: The name of a DNS server for the current zone, such as ns.magedu.com.;

Note: An area can have more than one NS record;

For example:

magedu.com. 86400 in NS ns1.magedu.com.

magedu.com. 86400 in NS ns2.magedu.com.

Mx:

Name: The region names of the current zone

Value: The host name of a mail exchanger in the current region;

Note: MX records can have multiple, but the value of each record should have a number indicating its priority;

For example:

Magedu.com. In MX ten mx1.magedu.com.

Magedu.com. In MX mx2.magedu.com.

A:

Name: An FQDN, such as www.magedu.com.

Value: a IPV4 address;

For example:

Www.magedu.com. In A 1.1.1.1

Www.magedu.com. In A 1.1.1.2

Bbs.magedu.com. In A 1.1.1.1

Aaaa:

Name:fqdn

Value:ipv6

Ptr:

Name:ip address, have a specific format, IP in turn, and add a specific suffix, such as 1.2.3.4 Records should be written as 4.3.2.1.in-addr.arpa.

Value:fqnd

For example:

4.3.2.1.in-addr.arpa. In PTR www.magedu.com.

CNAME:

Alias of the NAME:FQDN format;

Official name of the VALUE:FQDN format;

For example:

Web.magedu.com. In CNAME www.magedu.com.

Attention:

(1) TTL can be inherited from the global;

(2) @ Indicates the name of the current region;

(3) The adjacent two records whose name is the same, the following can be omitted;

(4) For the positive region, the value of the record of each mx,ns type is the FQDN, and this FQDN should have an a record;

DNS of Linux services (i)