tyt11fi.htm

一个学习tcp/ip协议的教程

<FONT COLOR=#000080>artemis     IN     A    143.23.25.7

merlin      IN     A    143.23.25.9

pepper      IN     A    143.23.25.72</FONT></PRE><P>The hostnames are not given as fully qualified domain names because the server can deduce the full name. If you want to use the full domain name, you must follow the name with a period. The machines shown in the preceding example would be given like this using fully qualified domain names:<BR><PRE>

<FONT COLOR=#000080>artemis.tpci.com.     IN     A    143.23.25.7

merlin.tpci.com.      IN     A    143.23.25.9

pepper.tpci.com.      IN     A    143.23.25.72</FONT></PRE><P>The Pointer (PTR) resource record is used to map an IP address to a name using IN-ADDR-ARPA. A single PTR RR helps make this clear. The record<BR><BR><PRE>

<FONT COLOR=#000080>7.0.120.147.in-addr.arpa IN PTR merlin</FONT></PRE><P>indicates that the machine named merlin has the IP address 147.120.0.7.<BR><P>The Name Server resource records point to the name server that has authority for a particular zone. Name Server (NS) records are used when a large network has several subnetworks, each with its own name server. An entry looks like this:<BR><BR><PRE>

<FONT COLOR=#000080>tpci.com   IN   NS  merlin.tpci.com</FONT></PRE><P>This record indicates that the DNS server for the tpci.com domain is called merlin.tpci.com. If there were several subnets used in tpci.com, there would be an NS RR for each subnet.<BR><BR><A ID=E70E44 NAME=E70E44></A><H5 ALIGN=CENTER><CENTER><FONT SIZE=4 COLOR=#FF0000><B>Completing the DNS Files</B></FONT></CENTER></H5><BR><P>As you saw earlier, DNS uses several files to hold resource records describing the zones used by DNS. The first file of interest is named.hosts, which contains the SOA, NS, and A resource records. All entries in the named.hosts file must begin in the first character position of each line. Here's a sample named.hosts file with comments added to show the records:<BR><PRE>

<FONT COLOR=#000080>; named.hosts files

; Start Of Authority RR

tpci.com.    IN    SOA     merlin.tpci.com

            root.merlin.tpci.com (

            2  ; Serial number

            7200 ; Refresh (2 hrs)

            3600 ; Retry (1 hr)

            151200 ; Expire (1 week)

            86400 ); min TTL

;

; Name Service RRs

tpci.com   IN   NS  merlin.tpci.com

subnet1.tpci.com IN NS goofy.subnet1.tpci.com

;