DNS是什么?
DNS(Domain Name System,域名系统)是互联网上最核心的带层级的分布式系统,它负责把域名转换为IP地址、反查IP到域名的反向解析以及宣告邮件路由等信息,使得基于域名提供服务称为可能,例如网站访问、邮件服务等。
DNS解析原理
DNS系统由两部分组成,一是Resolver解析器,作为DNS请求的客户端,负责从DNS记录中解析出IP或别名等信息;二是NS域名服务器,提供域名解析服务,例如Bind。
DNS服务器分为三类:一是权威域名服务器,用于解析域名或使用NS记录进行授权;二是缓存域名服务器,用于递归查询并缓存DNS记录;三是转发域名服务器,仅用于转发DNS请求给指定的上级域名服务器。
DNS记录类型
1.A记录:指定域名对应IP的记录
2.PTR记录:指定IP对应域名的记录
3.MX记录:邮件交换记录,也叫邮件路由记录,指向邮件服务器的IP
4.CNAME记录:别名记录,用于指向另一个域名
5.NS记录:域名服务器记录,指定该域名由哪个DNS服务器来解析
Bind部署DNS域名解析
Bind是什么?
BIND伯克利互联网域名服务(Berkeley Internet Name Domain)是一款全球互联网使用最广泛、能够提供安全可靠、快捷高效的域名解析的服务程序。
安装Bind服务程序
[root@localhost ~]# yum install -y bind-chroot
修改主配置文件
[root@localhost ~]# vim /etc/named.conf 12 options {13 listen-on port 53 { any; }; //监听53端口所有来源信息14 listen-on-v6 port 53 { ::1; };15 directory "/var/named";16 dump-file "/var/named/data/cache_dump.db";17 statistics-file "/var/named/data/named_stats.txt";18 memstatistics-file "/var/named/data/named_mem_stats.txt";19 allow-query { any; }; //允许所有来源访问
正向解析:由域名到IP
配置区域文件
[root@localhost ~]# vim /etc/named.rfc1912.zones zone "test.com" IN{type master; //服务器类型:主服务器file "test.com.zone"; // 数据文件名称allow-update {none;}; // 是否允许从服务器更新解析数据};
配置域名解析文件
[root@localhost ~]# cd /var/named [root@localhost named]# cp -a named.localhost test.com.zone [root@localhost named]# vim test.com.zone $TTL 1D@ IN SOA test.com. root.test.com. (0 ; serial1D ; refresh1H ; retry1W ; expire3H ) ; minimumNS ns.test.com. //域名服务器记录:表示该域名由哪台DNS进行解析ns IN A 192.168.41.10IN MX 10 mail.test.com. //邮箱交换记录,用于邮件系统解析mail IN A 192.168.41.10www IN A 192.168.41.10 //地址记录,表明三级域名www.test.com 对应的解析地址bbs IN A 192.168.41.10
重启服务,进行测试
[root@localhost named]# systemctl restart named[root@localhost named]# systemctl enable named[root@localhost ~]# nslookup //常用解析器> www.test.comServer: 192.168.41.10Address: 192.168.41.10#53Name: www.test.comAddress: 192.168.41.10> bbs.test.comServer: 192.168.41.10Address: 192.168.41.10#53Name: bbs.test.comAddress: 192.168.41.10>
#测试前记得修改DNS或者直接在/etc/resolve.conf中添加
反向解析:由IP到域名
配置区域文件
[root@localhost ~]# vim /etc/named.rfc1912.zones zone "41.168.192.in-addr.arpa" IN{type master;file "192.168.41.arpa";allow-update {none;};};
配置反向解析文件
[root@localhost ~]# cd /var/named [root@localhost named]# cp -a named.loopback 192.168.41.arpa [root@localhost named]# vim 192.168.41.arpa $TTL 1D@ IN SOA test.com. root.test.com. (0 ; serial1D ; refresh1H ; retry1W ; expire3H ) ; minimumNS ns.test.com.ns A 192.168.41.1010 PTR ns.test.com.10 PTR mail.test.com.10 PTR www.test.com.20 PTR bbs.test.com.
重启服务,进行测试
[root@localhost named]# systemctl restart named[root@localhost named]# nslookup> 192.168.41.10Server: 192.168.41.10Address: 192.168.41.10#5310.41.168.192.in-addr.arpa name = www.test.com.10.41.168.192.in-addr.arpa name = ns.test.com.10.41.168.192.in-addr.arpa name = mail.test.com.> 192.168.41.20Server: 192.168.41.10Address: 192.168.41.10#5320.41.168.192.in-addr.arpa name = bbs.test.com.>
部署从服务器
配置主服务器区域文件
[root@localhost named]# vim /etc/named.rfc1912.zones zone "test.com" IN{type master;file "test.com.zone";allow-update {192.168.41.30;}; //允许从服务器更新};zone "41.168.192.in-addr.arpa" IN{type master;file "192.168.41.arpa";allow-update {192.168.41.30;};};
配置从服务器区域文件
[root@localhost ~]# vim /etc/named.rfc1912.zones zone "test.com" IN{type slave; //服务器类型:从服务器masters {192.168.41.10;}; //主服务器IPfile "slaves/test.com.zone"; //同步的文件保存的地址};zone "41.168.192.in-addr.arpa" IN{type slave;masters {192.168.41.10;};file "slaves/192.168.41.arpa";};
重启服务,进行测试
[root@localhost slaves]# cd /var/named/slaves/[root@localhost slaves]# systemctl restart named[root@localhost slaves]# ls192.168.41.arpa test.com.zone // 主服务器数据文件已经同步过来了[root@localhost slaves]# nslookup > www.test.comServer: 192.168.41.30Address: 192.168.41.30#53Name: www.test.comAddress: 192.168.41.10> bbs.test.comServer: 192.168.41.30Address: 192.168.41.30#53Name: bbs.test.comAddress: 192.168.41.10> 192.168.41.10Server: 192.168.41.30Address: 192.168.41.30#5310.41.168.192.in-addr.arpa name = www.test.com.10.41.168.192.in-addr.arpa name = mail.test.com.10.41.168.192.in-addr.arpa name = ns.test.com.>
#测试前记得修改DNS或者直接在/etc/resolve.conf中添加
#同步之前记得设置或关闭主服务器防火墙,主从服务器都要重启named服务
几点说明
1./etc/resolve.conf是设置DNS的文件,解析器需要读取该文件请求DNS服务。
2.当网卡重启时,/etc/resolve.conf文件内的设置将会被网卡配置文件中的DNS设置覆盖,所以如果希望DNS设置永久生效,则要在网卡配置文件中配置DNS;如果只是临时修改或添加DNS,则直接配置/etc/resolve.conf文件即可。
3.Bind服务默认开启递归查询功能,所以既是缓存域名服务器,又是权威域名服务器。如果仅作为权威服务器用于域名解析,则可以关闭递归查询功能;
vim /etc/named.conf options {listen-on port 53 { any; };listen-on-v6 port 53 { ::1; };directory "/var/named";dump-file "/var/named/data/cache_dump.db";statistics-file "/var/named/data/named_stats.txt";memstatistics-file "/var/named/data/named_mem_stats.txt";allow-query { any; };recursion no; // 关闭递归查询功能dnssec-enable yes;dnssec-validation yes;
4.DNS服务器中存放着全球13组根域名服务器的NS记录,保存在域名解析文件named.ca中。
vim /etc/named.confzone "." IN {type hint;file "named.ca"; };vim /var/named/named.ca ; formerly NS.INTERNIC.NET ; . 3600000 NS A.ROOT-SERVERS.NET. A.ROOT-SERVERS.NET. 3600000 A 198.41.0.4 A.ROOT-SERVERS.NET. 3600000 AAAA 2001:503:ba3e::2:30 ; ; FORMERLY NS1.ISI.EDU ; . 3600000 NS B.ROOT-SERVERS.NET. B.ROOT-SERVERS.NET. 3600000 A 192.228.79.201 B.ROOT-SERVERS.NET. 3600000 AAAA 2001:500:84::b ; ; FORMERLY C.PSI.NET ; . 3600000 NS C.ROOT-SERVERS.NET. C.ROOT-SERVERS.NET. 3600000 A 192.33.4.12 C.ROOT-SERVERS.NET. 3600000 AAAA 2001:500:2::c "/var/named/named.ca" 92L, 3289C ... ...