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DNS的view设置

 在实际的网络应用中,我们有时希望对于同一个Domain Name能够根据不同的请求IP

地址/区域,解析到不同的对应IP地址,比如:有时对于企业内部网络和外部网络希望对同一域名解析到不同的IP地址以达到安全目的或者应用目的,又比如为了解决中国南北方电信/网通互访速度差异问题,您也会希望电信用户解析到的域名IP是位于电信网络中的服务器,网通用户亦然,使用户能够访问到临近的最快的服务器。

    而这些应用都可以通过对DNS的简单配置达到,使用DNS达到这一目的有以下的优点:

l  低成本-无需添加任何专用设备,只需通过简单配置即可; 

l  灵活性强-可随时增加/删除解析规则; 

l  有一定的可扩展能力-如果搭配Round Robin DNS可无缝快速的配置简单的负载均衡;

    下面,我们借助Bind 9(Bind 8没有这个功能哦)的这一特殊功能来实现域名的分离解析。在此例中,我们继续沿用x.centos.org作为域名,让局域网192.168.0.0/24内的机器除了192.168.0.40外都能解析到192.168.0.38,而192.168.0.40这台机器只能解析到192.169.0.39这个地址。

首先,需要修改named.conf文件,对view “internal”和view “external”这两个视图区域进行分别设置。我们将view “localhost_resolver”这个视图、key ddns key以及view视图内的slave这个区域都注释掉。然后,修改internal和external两个视图。

//

// Sample named.conf BIND DNS server ‘named‘ configuration file

// for the Red Hat BIND distribution.

//

// See the BIND Administrator‘s Reference Manual (ARM) for details, in:

//   file:///usr/share/doc/bind-*/arm/Bv9ARM.html

// Also see the BIND Configuration GUI : /usr/bin/system-config-bind and

// its manual.

//

options                

{

    // Those options should be used carefully because they disable port

    // randomization

           query-source    port 53;            

         // query-source-v6 port 53;     

        

         // Put files that named is allowed to write in the data/ directory:

         directory "/var/named"; // the default     

         dump-file                  "data/cache_dump.db"; 

        statistics-file  "data/named_stats.txt"; 

        memstatistics-file  "data/named_mem_stats.txt";

};

logging                

{

/*      If you want to enable debugging, eg. using the ‘rndc trace‘ command,

 *      named will try to write the ‘named.run‘ file in the $directory (/var/named).

 *      By default, SELinux policy does not allow named to modify the /var/named directory,

 *      so put the default debug log file in data/ :

 */

        channel default_debug {

                file "data/named.run";

                severity dynamic;

        };      

};

//

// All BIND 9 zones are in a "view", which allow different zones to be served

// to different types of client addresses, and for options to be set for groups

// of zones.

//

// By default, if named.conf contains no "view" clauses, all zones are in the

// "default" view, which matches all clients.

//

// If named.conf contains any "view" clause, then all zones MUST be in a view;

// so it is recommended to start off using views to avoid having to restructure

// your configuration files in the future.

//

#view "localhost_resolver"     

#{

/* This view sets up named to be a localhost resolver ( caching only nameserver ).

 * If all you want is a caching-only nameserver, then you need only define this view:

 */

#       match-clients                   { localhost; };     

#       match-destinations        { localhost; };    

#       recursion yes;                   

         # all views must contain the root hints zone:

#       include "/etc/named.root.hints";

 

        /* these are zones that contain definitions for all the localhost

         * names and addresses, as recommended in RFC1912 - these names should

          * ONLY be served to localhost clients:

          */

#       include "/etc/named.rfc1912.zones";

#};

view "internal"          

{

/* This view will contain zones you want to serve only to "internal" clients

   that connect via your directly attached LAN interfaces - "localnets" .

 */

         match-clients           { 192.168.0.40; };  //设置internal区域由192.168.0.40这个地址解析。

#       match-destinations        { localnets; };

         recursion yes;

         // all views must contain the root hints zone:

         include "/etc/named.root.hints";

 

    include "/etc/named.rfc1912.zones";  //将internal视图的区域定义文件包含进来。

         // you should not serve your rfc1912 names to non-localhost clients.

 

         // These are your "authoritative" internal zones, and would probably

         // also be included in the "localhost_resolver" view above :

 

         zone "my.internal.zone" {                 

                   type master;

                   file "my.internal.zone.db";

         };

#       zone "my.slave.internal.zone" {            

#                type slave;

#                file "slaves/my.slave.internal.zone.db";

#                masters { /* put master nameserver IPs here */ 127.0.0.1; } ;

                   // put slave zones in the slaves/ directory so named can update them

#       };     

#       zone "my.ddns.internal.zone" {          

#                type master;

#                allow-update { key ddns_key; };

#                file "slaves/my.ddns.internal.zone.db";

                   // put dynamically updateable zones in the slaves/ directory so named can update them

#       };                        

};

#key ddns_key  

#{

#       algorithm hmac-md5;

#       secret "use /usr/sbin/dns-keygen to generate TSIG keys";

#};

view    "external"                   

{

/* This view will contain zones you want to serve only to "external" clients

 * that have addresses that are not on your directly attached LAN interface subnets:

 */

         match-clients           { !192.168.0.40;192.168.0.0/24;  }; //设置external视图由192.168.0.0

这个网段的机器解析,但

192.168.0.40这台主机不能解析。

#       match-destinations        { any; };

 

         recursion no;

         // you‘d probably want to deny recursion to external clients, so you don‘t

        // end up providing free DNS service to all takers

 

         // all views must contain the root hints zone:

         include "/etc/named.root.hints";

    include “/etc/named.other.zones”;   //添加external的区域定义文件,文件名随意。

         // These are your "authoritative" external zones, and would probably

        // contain entries for just your web and mail servers:

 

         zone "my.external.zone" {

                   type master;

                   file "my.external.zone.db";

         };

};

接下来,修改internal和external视图的区域定义文件。首先,修改internal区域定义文件named.rfc1912.zones,根据需要添加正向和反响解析区域。

zone "centos.org" IN {        

         type master;           

         file "centos.org.zone";    

         allow-update { none; };  

};

 

zone "0.168.192.in-addr.arpa" IN { 

         type master;              

         file "0.168.192.zone";        

         allow-update { none; };

};

下面,将named.rfc1912.zones文件复制一份,并更名为named.other.zones(这个文件名要和named.conf里相应视图内的文件定义要一致哦!)。然后,对named.other.zones文件进行修改。

zone "centos.org" IN {        

         type master;           

         file "centos.org1.zone";    //这里修改external的正向解析文件为centos.org1.zone。

         allow-update { none; };  

};

 

zone "0.168.192.in-addr.arpa" IN { 

         type master;              

         file "0.168.1921.zone";     //这里修改external的反向解析文件为0.168.1921.zone。

         allow-update { none; };

};

下面,对区域定义中定义的文件进行配置。下面是internal的区域解析文件:

$TTL          86400                                    

@              IN SOA      x.centos.org.  root.x.centos.org. (

                                     2009101901     ; serial (d. adams)  

                                               3H             ; refresh         

                                               15M          ; retry          

                                               1W            ; expiry          

                                               1D )           ; minimum      

                 IN NS                  x.centos.org.         

            IN MX       mail.centos.org.       

X                IN A               192.168.0.39        

www        IN CNAME   x.centos.org.   //此为正向解析文件

———————————————————————————————————————

$TTL          86400                                    

@              IN SOA      x.centos.org.  root.x.centos.org. (

                                     2009101901     ; serial (d. adams)  

                                               3H             ; refresh          

                                               15M          ; retry           

                                               1W            ; expiry         

                                               1D )           ; minimum      

                 IN NS                  x.centos.org.  

39          IN PTR       x.centos.org.   //此为逆向解析文件

这里,internal的正向解析文件为centos.org.zone,逆向解析文件为0.168.192.zone;external的正向解析文件为centos.org1.zone,逆向解析文件为0.168.1921.zone。两个视图的解析文件配置方法一样,只是IP地址不同。可以先将internal的解析文件配置好,然后复制一份并更名,然后稍作修改即可。

一切修改完毕后,重启DNS服务器,然后进行测试即可。

DNS的view设置