Installing and Administering Internet Services

76 Chapter3

Conﬁguring and Administering the BIND Name Service

Overview of the BIND Name Service

The DNS Notify feature is enabled in the master server by default. In

some environments, the master server in a zone might be an 8.1.2 server

with DNS notify enabled, while the other servers in the zone are 4.x

servers (without the DNS notify feature). In such environments,

whenever the master changes and sends a notiﬁcation to the other

servers, the 4.x servers will ignore this notiﬁcation as they do not

understand the notify protocol.

How BIND Works

When a user who is logged into host venus in the nmt.edu domain types

the following command,

telnet indigo.div.inc.com

the following events occur:

1. The telnet process calls gethostbyname to get the internet address

of indigo.div.inc.com.

2. The gethostbyname routine invokes the BIND resolver, a set of

routines for querying name servers.

3. The resolver constructs a query and sends it to a name server. If the

local host is not running a name server, it should have a ﬁle called

/etc/resolv.conf, which contains one or more internet addresses

for name servers that serve the local domain. If the local host does not

have an /etc/resolv.conf ﬁle, the resolver sends the query to the

local name server.

4. The name server daemon, named, receives the query from the

resolver. Since the name server has information about only the hosts

in its local domain (nmt.edu), it cannot answer the query with the

information in its local database.

5. The local name server queries a root name server to ﬁnd the address

of indigo.div.inc.com. A root name server serves the root domain.

It typically stores information about hosts and name servers one and

two levels below the root.

6. If the root name server cannot resolve the host name, it returns the

address of a name server for the inc.com domain.

7. The local name server queries the server for the inc.com domain to

ﬁnd the address of indigo.div.inc.com.

8. The name server for the inc.com domain may not have information