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

Brief introduction of DNS forward Analytical experiment DNS 1. The function of DNS

Forward resolution: look up the IP address according to the domain name, and resolve the specified domain name to the corresponding IP address.

Reverse resolution: look up the domain name according to the IP address, and resolve the specified IP address to the corresponding domain name.

> 2. DNS system type

Cache domain name server: also known as cache server, which obtains the domain name and IP address records by querying other domain name servers, and then caches the domain name query results locally to improve the speed of repeated queries.

Primary domain name server: the official server of a specific DNS region, which is unique. Responsible for maintaining the mapping records of all domain names and IP addresses in this area.

Slave domain name server: also known as the secondary domain name server, the domain name and IP address records maintained by the slave domain name server come from the primary domain name server.

3. Hierarchical structure of DNS domain name resolution service

Here we take the domain name of Baidu as an example to explain in detail.

Our common Baidu domain name is www.bai.com, but its complete domain name should be www.baidu.com. Let's introduce it from back to front.

".": root domain: at the top of the domain name space.

".com": top-level domain: generally represents a type of organization or national region.

".baidu": secondary domain: used to identify a specific organization within the top-level domain.

"www": hostname: the host is located at the lowest level of the domain name space, which is a specific computer.

Experimental operation

Remember to check the bind configuration file after installing the bind package, which is closely related to our later experiments. Don't pay attention to the following files. / etc/named/conf--bind main configuration file

/ etc/named.rfc1912.zones--bind zone profile

/ var/named/named.localhost--bind zone data configuration file

In the first step, we first go to the main configuration file of bind to modify it. (vim / etc/named.conf)

Change the listening address to the local IP address: 192.168.131.133

Change the user that allows DNS resolution here in bind to all: any

According to the order of our bind configuration files, we are going to go to the bind zone configuration file to modify it. (vim / etc/named.rfcc1912.zone)

There are templates for forward and reverse resolution of DNS in the zone configuration file. Here, we copy a forward template to the following, modify the template, change the domain name to yun.com, and set the zone data configuration file to yun.com.zone to facilitate identification.

The zone profile has also been configured, so here is the configuration of the zone data profile. But because our yun.com zone data configuration file is newly created by us, there is nothing in it, so we need to copy a data configuration file to yun.com.zone, but remember to keep the permissions of the file, and then go to the zone data configuration file to modify it.

After changing @ in the first line to a domain name and entering the administrator's mailbox, change @ to the domain name and enter the host IP address, and then configure the domain name resolution. After br/ >, change @ to the domain name and enter the host IP address, and then configure the domain name resolution.

Www IN A 192.168.100.99 (IP address for hostname resolution)

Ftp IN A 192.168.100.88 (IP address for ftp domain name resolution)

Smtp IN A www (IP address for host alias resolution)

IN A 8.8.8.8 (IP address to which the pan-domain name is resolved)

Turn off the firewall and enhanced security features

Systemctl stop firewalld.service

Setenforce 0

After the named service is configured, you can start the named service and check whether the named service is running properly.

The DNS server needs to have a fixed IP address. Here we write the native IP address to the domain name resolution configuration file as the default IP address of the DNS server.

Finally, we can use the host command to verify the DNS parsing service.

Host www.yun.com (resolve the primary domain name)

Host smtp.yun.com (validate alias resolution)

Host ftp.yun.com (ftp domain name resolution)

Host * .yun.com (pan-domain name resolution verification)

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