• FQDN(Full Qualified Domain Name), Complete Qualified Domain Name

  • Website name = server name. Domain name suffix
  • www.pku.edu.cn = site name. ***. secondary domain. primary domain

• All complete domain names will end with. (dots):

              Root domain .
    ┌─────┬─────┼─────┬─────┬─────┬──────┬─
  .com   .cn   .us   .tw   .kr   .hk   .......  #Level 1 DNS Server
    ┌─────┴────┬─────────┬─────────┬─
  .com.cn   .net.cn   .org.cn  .edu.cn          #Secondary DNS Server
    ├─────────────────┬───────────────┬─
  .lala.com.cn   .haha.com.cn   .xixi.com.cn    #Three Level DNS Server
        ├─────────────────────┬─
    web1.lala.com.cn    tts.lala.com.cn         #Full host name
  

• Common top-level domain names/first-level domain names:

  Country/region	.cn	.us	.kr	.hk	.tw	...
  Organizational domain	.com	.net	.edu	.org	.gov	...

DNS parsing library

• Resource record: rr(resource record), with the concept of type; properties used for parsing this record.

  | Resource Record | Name | Meaning| | ------------ | ------------ | ------------ | A | Address address IPv4 | This record lists IP addresses for specific host names AAAA | Address address IPv6| NS | Name Server Domain Name Server | This record specifies the name server responsible for a given region SOA | Start of Authority authorization status| MX | Mail Exchanger mail exchange | This record lists the hosts responsible for receiving e-mail sent to the domain CNAME | Canonical Name specification name | This record specifies an alias for the standard host name PTR | Pointer pointer|

DNS query process

• DNS query mechanism:

  • Recursive Query
    • The preferred DNS server, running to the corresponding other DNS servers, will ask the final results back to the process
    • Client interacting with preferred DNS server
    • Open recursive queries by default (recursion yes|no)
  • Iterative Query
    • The preferred DNS server interacts with other DNS servers

• DNS query order:

    1. Local hosts file 2, Local DNS cache 3, Local DNS server 4, Initiate iteration query
  

I. Building Basic DNS Server

svr7.test.cn  ---> 192.168.4.7
pc207.test.cn ---> 192.168.4.207
www.test.cn   ---> 192.168.4.100

Server (192.168.4.7)

1. Installation of software packages

]# yum -y install bind bind-chroot

2. Modify configuration files

]# vim /etc/named.conf
options {
    listen-on port 53 { 192.168.4.7; };   #The address and port of the listening server
    directory    "/var/named";            #By default, specify the address library file storage path
    allow-query  { any; };                #Allow any client to query
};
zone    "test.cn"    IN {          #Specify the domain name to be resolved locally
    type    master;                #Specify native as authoritative master DNS server
    file    "test.cn.zone";        #Specify the address library file as test.cn.zone
};

]# named-checkconf /etc/named.conf  #Check configuration file syntax

3. Establishing Address Area File

]# cd /var/named/                           #Preparing template files
]# cp -p named.localhost test.cn.zone       #Privilege Attribute Invariant Copy Template
]# ls -l test.cn.zone
-rw-r----- 1 root named 152 6 January 21, 2007 test.cn.zone

]# vim test.cn.zone                 #Editing area files
$TTL 1D                                 ;TTL=Time To Live=survival time
@   IN SOA  @ rname.invalid. (          ;SOA=Start Of Authority=Authorization information begins,@Regional name
                    0   ; serial，serial number        ;semicolon; The beginning part represents a comment
                    1D  ; refresh，Refresh time
                    1H  ; retry，Retry interval
                    1W  ; expire，Expiration time
                    3H )    ; minimum，Negative when unanswerable TTL value
test.cn.   NS  svr7          ;NS=NameServer，statement test.cn.Domain name DNS The server is svr7.test.cn.
svr7       A   192.168.4.7   ;Appoint svr7.test.cn.Of ip Address 192.168.4.7
www        A   1.1.1.1    
ftp        A   2.2.2.2

]# named-checkzone test.cn test.cn.zone     #Check configuration file, command area name configuration file
zone test.cn/IN: loaded serial 0
OK                                         #Examination result ok

4. Enabling Services

]# systemctl restart named
]# systemctl enable named

Client

1. Setting up DNS Server

]# echo 'nameserver    192.168.4.7 > /etc/resolv.conf'

2. Detecting domain name resolution

• host

  ]# host svr7.test.cn
  svr7.test.cn has address 192.168.4.7
  

• nslookup

  ]# nslookup www.test.cn
  Server:		192.168.4.7
  Address:	192.168.4.7#53
  Name:	www.test.cn
  Address: 1.1.1.1
  

II. Multilateral DNS Services

1. Modify the configuration file (following example 192.168.4.7)

]# vim /etc/named.conf          #Additional new areas
zone  "qq.com"   IN  {
    type master;
    file  "qq.com.zone";
};

2. Editing area files

]# cp -p /var/named/test.cn.zone /var/named/qq.com.zone
]# vim qq.com.zone
$TTL 1D
@   IN SOA  @ rname.invalid. (
                    0   ; serial
                    1D  ; refresh
                    1H  ; retry
                    1W  ; expire
                    3H )    ; minimum
qq.com.  NS  svr7   
svr7     A   192.168.4.7
www      A   3.3.3.3
ftp      A   4.4.4.4

3. Restart service

]# systemctl restart named

4. Client Testing

]# nslookup www.qq.com
Server:		192.168.4.7
Address:	192.168.4.7#53
Name:	www.qq.com
Address: 3.3.3.3

III. Special Analytical Records

Connect with the preceding example

1. Load balancing based on DNS domain name:

#Server
]# vim qq.com.zone
$TTL 1D
@   IN SOA  @ rname.invalid. (
                    0   ; serial
                    1D  ; refresh
                    1H  ; retry
                    1W  ; expire
                    3H )    ; minimum
qq.com.  NS    svr7 
svr7      A    192.168.4.7
www       A    192.168.4.11         ;To configure www Load balancing
www       A    192.168.4.12
www       A    192.168.4.13
ftp       A    4.4.4.4

]# systemctl restart named

#Client Testing
]# nslookup www.qq.com
Server:		192.168.4.7
Address:	192.168.4.7#53
Name:	www.qq.com
Address: 192.168.4.12
Name:	www.qq.com
Address: 192.168.4.13
Name:	www.qq.com
Address: 192.168.4.11

2. Pan-domain name resolution:

The server:
]# cd /var/named
]# vim qq.com.zone
$TTL 1D
@   IN SOA  @ rname.invalid. (
                    0   ; serial
                    1D  ; refresh
                    1H  ; retry
                    1W  ; expire
                    3H )    ; minimum
qq.com.  NS    svr7
svr7      A    192.168.4.7
www       A    192.168.4.11
www       A    192.168.4.12
www       A    192.168.4.13
ftp       A    4.4.4.4
*         A    1.2.3.4            ;Pan-domain Name Resolution
]# systemctl restart named

//Client:
]# host ftp.qq.com
ftp.qq.com has address 4.4.4.4
]# host fan.qq.com
fan.qq.com has address 1.2.3.4

3. Regular pan-domain name resolution:

web1.qq.com------>192.168.10.1
web2.qq.com------>192.168.10.2
web3.qq.com------>192.168.10.3
web4.qq.com------>192.168.10.4
......
web50.qq.com------>192.168.10.50

Function: $GENERATE generates continuous range numbers

The server:
]# cd /var/named/
]# vim qq.com.zone
$TTL 1D
@   IN SOA  @ rname.invalid. (
                    0   ; serial
                    1D  ; refresh
                    1H  ; retry
                    1W  ; expire
                    3H )    ; minimum
qq.com.  NS    svr7
svr7      A    192.168.4.7
www       A    192.168.4.11
www       A    192.168.4.12
www       A    192.168.4.13
ftp       A    4.4.4.4
*         A    1.2.3.4            ;Pan-domain Name Resolution
$GENERATE  1-50  web$   A   192.168.10.$    ;Use $GENERATE Function Generation Regular Pan-domain Name Resolution

]# systemctl restart named

#Client
]# host web.qq.com
web.qq.com has address 1.2.3.4
]# host web1.qq.com
web1.qq.com has address 192.168.10.1
]# host web11.qq.com
web11.qq.com has address 192.168.10.11
]# host web50.qq.com
web50.qq.com has address 192.168.10.50

IV. Subdomain Authorization of DNS

Connect with the preceding example

Parent domain www.test.cn svr7 server 192.168.4.7
 Subdomain www.bj.test.cn Beijing Branch pc207 Server 192.168.4.207

• Family Host Configuration Subdomain Authorization (192.168.4.7)

  ]# cd /var/named
  ]# vim  test.cn.zone
  test.cn.     NS   svr7
  bj.test.cn.  NS   pc207.bj            ;Designated subdomain DNS The server
  svr7         A    192.168.4.7
  pc207.bj     A    192.168.4.207 
  www          A    1.1.1.1    
  ftp          A    2.2.2.2
  ]# systemctl restart named
  

• Subdomain Host Configuration (192.168.4.207)

  ]# yum -y install bind bind-chroot      #Installation software
  ]# vim /etc/named.conf                  #Modify configuration files
  options  {
      directory  "/var/named";
  };
  zone  "bj.test.cn"   IN  {      ;Resolving Subdomain Domain Names
      type  master;
      file  "bj.test.cn.zone";
  };
  ]# cd /var/named
  ]# cp -p named.localhost bj.test.cn.zone
  ]# vim bj.test.cn.zone       #Editing area files
  $TTL 1D
  @   IN SOA  @ rname.invalid. (
                      0   ; serial
                      1D  ; refresh
                      1H  ; retry
                      1W  ; expire
                      3H )    ; minimum
  bj.test.cn.   NS  pc207             ;Setting up Domain Server
  pc207         A   192.168.4.207   
  www           A   11.12.13.14
  ]# systemctl restart named              #Restart service
  ]# systemctl enable named
  

• test

  ]# nslookup www.bj.test.cn 192.168.4.207
  Server:		192.168.4.207
  Address:	192.168.4.207#53
  Name:	www.bj.test.cn
  Address: 11.12.13.14
  

5. Caching DNS

• Function: Accelerate the parsing process, so that the client can get the parsing results as soon as possible.

• Software package: bind bind-chroot

• mode

  • Global forwarding:

    • Forward the request to the designated public DNS (other cached DNS), requesting recursive service.

  • Root domain iteration:

    • Iterate to the DNS server of the root, first and second level domains in turn.

• Example:

  • Idea: 192.168.4.254 serves as a cache DNS server, and the real DNS is 172.40.1.10.

  1. Installation of software packages

  ]# yum -y install bind bind-chroot
  

  2. Editing configuration files

  ]# cat /etc/resolv.comf
  nameserver 172.40.1.10
  
  ]# vim /etc/named.conf
  options {
      directory    "/var/named";
      forwarders    { 172.40.1.10; };     #Designate 172.40.1.10 parsing when there is no corresponding parsing in the local cache
  };
  ]# systemctl restart named
  

  3. Client. Virtual Machine Usage Resolution

  ]# nslookup www.360.com 192.168.4.254
  

6. Split Separation and Analysis

• Let the client access the nearest server in the network.
• When different types of clients request to parse the same domain name, they get different parsing results (Ip).
• When receiving DNS query requests from clients, it can distinguish the source addresses of clients and provide different parsing results (IP addresses) for different types of clients.

BIND view View

• Clients are categorized according to the set of source addresses, and different clients get different results (different treatment).

  • Note: Clients are properly categorized (all clients need to find the corresponding categorization)
  • Note: Matching from top to bottom stops
  • Note: All zone s must be in the view field

• Format:

  view    "View Name"    {
   match-clients    { IP; }    //Matching Client Address
   zone    "Resolved domain name" {
   ...    Address Library 1;
   }
  };
  

  view   "nsd"    {
   match-clients   {  192.168.4.207;  }   #Match the address of the client
   zone "test.cn"    {
   ...... Address Library 1;
  }; };
  
  view   "abc"   {
   match-clients  {   any;   }             
   zone "test.cn"    {                           
   ...... Address Library 2;
  }; };
  

• Examples, environment and requirements:

  • Authoritative DNS: svr7.test.cn 192.168.4.7
  • Responsible area: test.cn
  • A Record Separation and Resolution: A Case Study of www.test.cn
  • The client's parsing results:
    • 192.168.4.207 -----> 192.168.4.100
    • Other Address - ----> 1.2.3.4

  Operational steps
  
  //Virtual Machine A
  1.Modify configuration files/etc/named.conf
  view  "nsa"  {
      match-client  { 192.168.4.207; };
      zone  "test.cn"  {
      type    master;
      file    "test.cn.nsd";
      };
  };
  view  "abc"  {
      match-client  { any; };
      zone  "test.cn"  {
      type  master;
      file  "test.cn.abc";
      };
  };
  
  2.Establishing Address Library Files
  ]# vim /var/named/test.cn.nsd
  test.cn.    NS   svr7
  svr7        A    192.168.4.7
  www         A    192.168.4.100
  ]# vim /var/named/test.cn.abc
  test.cn.    NS   svr7
  svr7        A    192.168.4.7
  www         A    1.2.3.4
  
  3.restart named service
  ]# systemctl restart named
  
  4.In Virtual Machine A,B Separate test analysis
  
  

7. DNS Cache Use Variables

]# vim /etc/named.conf
options {
    directory    "/var/named";
};
acl Variable name { Address 1; Address 2; Address 3; Address 4;...};
view "nsd" {
    match-clients { Variable name; };
    zone "test.cn" {
    type    master;
    file    "test.cn.nsd";
    };
};
view "abc" {
    match-clients { any; };
    zone "test.cn" {
    type    master;
    file    "test.cn.abc";
    };
};