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。