The root name servers contain information about where the authoritative name servers for each of the top-level zones are situated. Given a query about a domain name, the root name servers provide at least the names and addresses of the name servers that are authoritative for the top-level zone that the domain name ends with. The top-level name servers also provide the list of the authoritative name servers for the second-level zone that the domain name ends with. Every query to the name server provides information about how to reach the final destination, or provides the actual answer.
If you are connected to the Internet, you can use the root servers already available (For a list of root servers, use anonymous ftp to get the file /domain/named.root from rs.intenic.net.) However, if you are on an isolated network, you must set up your own root servers.
A root server does not have a cache entry in its configuration file. Instead, it has an entry like the following, which indicates that the server is a master for the root domain:
zone “.” {
type master;
file “db.root”;
}; |
The db.root file typically contains only NS and A resource records for the authoritative name space tree. You can use the hosts_to_named command with the -r option to create the db.root file. For more information, type man 1M hosts_to_named at the HP-UX prompt.
The db.cache file on the other name servers in the domain must contain an entry for this root server.
A domain can have more than one root name server.
Following is an example of the root zone file, db.root. In the example db.root file, hosts rabbit.div.inc.com, denny.dept.inc.com, and sally.doc.inc.com are authoritative name servers for the root domain. Hosts eduardo.inc.com and labs.inc.com are authoritative for the inc.com subdomain.
@ IN SOA rabbit.div.inc.com. root.moon.div.inc.com. (
3 ; Serial
10800 ; Refresh after 3 hours
3600 ; Retry after 1 hour
604800 ; Expire after 1 week
86400 ) ; Minimum ttl of 1 day
IN NS rabbit.div.inc.com.
IN NS denny.dept.inc.com.
IN NS sally.dept.inc.com.
rabbit.div.inc.com. 86400 IN A 15.19.8.119
denny.dept.inc.com. 86400 IN A 15.19.15.33
sally.doc.inc.com. 86400 IN A 15.19.9.17
; ; set ttl to 3 days ;
inc.com. 259200 IN NS eduardo.inc.com.
2592 IN NS labs.inc.com.
15.in-addr.arpa. 259200 IN NS eduardo.inc.com.
259200 IN NS labs.inc.com.
eduardo.inc.com. 259200 IN A 15.19.11.2
labs.inc.com. 259200 IN A 15.19.13.7 |
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