Network setup - How to - Routers - Cisco - Linux

About DNS

In most modern networks, including the Internet, users locate websites by domain name (eg www.google.com), this allows the user to access millions of web pages on the Internet without having to remember each and every one of the IP addresses associated with the name of the page you wish to visit. One way to solve this problem is by complementation of a mechanism that when a user asks for the name of a website this server knows which IP address belongs to the website by which user questions. The mechanism which we speak is a name server mostly known as DNS (Domain Name Server). Likewise, a DNS server has the function of storing information associated with existing domain names by which the user question, for example:

www.gmail.com
www.ipnetworksetup.com
www.yahoo.com

Therefore, the DNS server is able to associate different types of information on each name, the most common uses are the allocation of domain names to IP addresses and the location of the mail servers for each domain. When a client requests information from a nameserver, it usually connects to port 53. Falsely DNS is associated with a database, which is completely false, because the fundamental principles of the specified databases that can not contain redundant data ie the data can not be the same information which is stored several times in the same database mapping names to IP addresses is certainly the best known feature of the DNS servers. For example, if the IP address for the site www.cisco.com is 23.5.144.170, most people to access it in a web browser type in the web address www.cisco.com and not the IP address.

The institution responsible for assigning domain names on the Internet is known as a NIC (Network Information Center). This institution is responsible for assigning domain names on the Internet, whether generic domain names or countries, allowing individuals or companies websites by riding through an ISP using a DNS. Technically there is a NIC for every country in the world and each of these is responsible for all domains with the ending for your country. For example: NIC Mexico is the entity responsible for managing all domains terminated ".mx", which is the corresponding termination domains assigned to Mexico. FQDN (Fully Qualified Domain Name) is an unambiguous domain name that specifies the absolute position of the node in the hierarchical tree of the DNS. It is distinguished from a regular name because it has a point at the end

Components of a DNS

A DNS is composed of three basic components, which are:

1. DNS Client
2. DNS Server
3. Authority Zones

1 DNS Client

When we speak of DNS client, we refer to the host or user making the request, that is, to the user's computer which generates the request to the DNS asking for the name of an existing domain on the Internet.

2 DNS Server

There are 3 basic types of DNS servers which are:

• Master Server
• Slave Server
• Cache Server

Primary or Master server

A master DNS server stores the original zone records and authority. Besides the master DNS server is responsible for responding to requests made by other DNS servers

Secondary or Slave Server

A slave DNS server also has the ability to respond to requests made by a DNS client and another DNS server, the difference is that the slave servers get the information about the domain names from the master servers

Cache Server

This provides name resolution services in response to requests from DNS clients, these name resolution services are saved certain time in order to access this information quickly. This server type has no authority over the areas of authority. DNS servers are responsible for making product queries requests requested by DNS clients. DNS server for it makes use of two types of queries:

-Iterative Queries
-Recursive Queries

-Recursive Queries

An iterative query works as follows: Imagine that we have a DNS client who makes the request to our server dns-1 on the domain "www.ejemplo.com" our dns server-1 does not know who is "www.sample . com "but he knows who can have that domain so now dns-1 makes a request to dns-2, dns-2 responds to dns-1 does not know who is" www.ejemplo.com "but he know who might have that domain registered, so now dns-2 makes a request to dns-3, then dns-3 responds the request made by dns-2 replying that if you know who is "www.ejemplo.com" so dns-3 sends the IP address associated with "www.ejemplo.com" to dns-2, dns-2 answers the request to dns-1, and dns-1 in turn responds to the DNS client.

-Iterative Queries

A recursive query works as follows: Imagine that we have a DNS Client who makes the request to our server dns-1 on the domain "www.ejemplo.com" our dns server-1 does not know who is "www.sample . com" but he knows who can have that domain so dns-1 responds to the DNS Client to ask the dns-2, dns-2 does not know who is "www.ejemplo.com" but he knows who may have that domain so dns-2 responds to the DNS Client to ask the dns-3, dns-3 knows who "www.ejemplo.com" so dns-3 responds to the request by returning DNS Client the IP that corresponds to "www.ejemplo.com".

Differences between Iterative Queries against Recursive Queries

The differences between iterative queries against recursive queries are: When making iterative queries, who assumes all the burden is our DNS client (our machine). When making recursive queries who assumes all load is the DNS server as he is responsible to provide a complete response to the request made by the DNS Client. Knowing this information, one can conclude that recursive queries are better than iterative queries because recursive queries take away from our Client DNS (our machine) to the task of responding to requests sought by himself, making the whole load is assumed by the DNS server.

3 Authorities Zones

Authorities zones contain the features on which our domain act, it configures the important aspects and options specific area, these areas made ​​configurations are loaded from the master server. The information in each Authority Zone is stored locally in a file on the DNS server.