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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