Difference between zone and a Domain ?

luke79 · 05-28-2015, 11:11 AM

I am learning the basics of DNS. Will be installing BIND packages soon in RHEL 6.5 soon.

2 basic questions

hewrac214.hk.citibank.com is a DB server running in a company. Which part of this hostname is the domain and which one is the zone ?

Similarly, In https://mail.yahoo.com , which one is domain and which one is a zone ?

smallpond · 05-28-2015, 11:38 AM

Quote:

Originally Posted by luke79

I am learning the basics of DNS. Will be installing BIND packages soon in RHEL 6.5 soon.

2 basic questions

hewrac214.hk.citibank.com is a DB server running in a company. Which part of this hostname is the domain and which one is the zone ?

Similarly, In https://mail.yahoo.com , which one is domain and which one is a zone ?

mail.yahoo.com, yahoo.com, and com are all domains.
yahoo.com, com and '.' (the root zone) are all DNS zones.

luke79 · 05-29-2015, 04:14 AM

Bit confusing.

What about hewrac214.hk.citibank.com or just hewrac214.citibank.com?

wildwizard · 05-29-2015, 04:51 AM

Your confusion stems from a lack of understanding of what the two terms mean

domain - Is simply a string of text
zone - Is an administrative construct

In your second example

Code:

hewrac214.hk.citibank.com
hewrac214.citibank.com

citibank.com could be the zone for both or it may only be for the second entry, only citibank would know as they get to decided how their domain (citibank.com) is administered

luke79 · 06-02-2015, 04:54 AM

citibank.com could be the zone for both or it may only be for the second entry, only citibank would know as they get to decided how their domain (citibank.com) is administered

I am still confused on this. Can you or anyone point me to a URL where this is explained well.
There are thousands of web pages explaining Domains and zones in the Internet. But not for a host like hewrac214.citibank.com in the Intranet . hewrac214.citibank.com being a hypothetical DB server in citibank's datacenter

wildwizard · 06-02-2015, 07:31 PM

The source for this is RFC 1034 Section 4.2

Quote:

4.2 How the database is divided into zones

The domain database is partitioned in two ways: by class, and by "cuts"
made in the name space between nodes.

The class partition is simple. The database for any class is organized,
delegated, and maintained separately from all other classes. Since, by
convention, the name spaces are the same for all classes, the separate
classes can be thought of as an array of parallel namespace trees. Note
that the data attached to nodes will be different for these different
parallel classes. The most common reasons for creating a new class are
the necessity for a new data format for existing types or a desire for a
separately managed version of the existing name space.

Within a class, "cuts" in the name space can be made between any two
adjacent nodes. After all cuts are made, each group of connected name
space is a separate zone. The zone is said to be authoritative for all
names in the connected region. Note that the "cuts" in the name space
may be in different places for different classes, the name servers may
be different, etc.

These rules mean that every zone has at least one node, and hence domain
name, for which it is authoritative, and all of the nodes in a
particular zone are connected. Given, the tree structure, every zone
has a highest node which is closer to the root than any other node in
the zone. The name of this node is often used to identify the zone.

It would be possible, though not particularly useful, to partition the
name space so that each domain name was in a separate zone or so that
all nodes were in a single zone. Instead, the database is partitioned
at points where a particular organization wants to take over control of
a subtree. Once an organization controls its own zone it can
unilaterally change the data in the zone, grow new tree sections
connected to the zone, delete existing nodes, or delegate new subzones
under its zone.

If the organization has substructure, it may want to make further
internal partitions to achieve nested delegations of name space control.
In some cases, such divisions are made purely to make database
maintenance more convenient.

joec@home · 06-06-2015, 07:38 PM

While not exactly by the book, another way to think of it is that a domain is the namespace itself, where as the zone is the detailed information about a domain. That is to say yahoo.com is a domain. The information that tells what name inside of yahoo.com details to what IP address and other information is the zone of yahoo.com. I have a box full of apples. The box is the domain, the apples are the zone information.

root nameservers are known and not named, per say, meaning the .com domain is not preceded by a name such as com.rootnameservers

.com is one of many TLD's (Top Level Domains) hosted by the root nameservers

yahoo.com is a hosted domain of the TLD .com nameservers

sports.yahoo.com is a subdomain hosted by the nameservers hosting yahoo.com domain zone file

A simple zone file would be something like the following. Note: This is not exact, wanting to type out a real zone file here but has the general information.

SOA ns1.example.com {bunch of other information here} ;states that ns1.example.com is the primary nameserver
NS ns1.example.com. ; is a public nameserver with this information available
NS ns2.example.com. ; is another public nameserver with this information available
MX mail.example.com. ; send inbound mail here
A ns1 12.34.56.253 ; ip address of ns1.example.com. Note it does not end with a "." so example.com is appended
A ns1 12.34.56.254 ; ip address of ns2.example.com
A example.com. 12.34.56.100 ; ip address
A www 12.34.56.100 ; ip address
A mail 12.34.56.200 ; inbound mail server described in the MX record

In order for this to work, the TLD needs to have in its own zone file

NS ns1.example.com.
NS ns2.example.com.
A ns1.example.com. 12.34.56.253
A ns1.example.com. 12.34.56.254

And for this to work the rootname servers need to have in their zone file

NS ns1.somedomain.com. ; whoever is in charge of .com that year
NS ns2.somedomain.com.
A ns1.somedomain.com. 45.34.56.253 ; and what ever ip addresses those nameservers are hosted on
A ns1 .somedomain.com. 45.34.56.254

Also, look into the dig command. Very important tool!

10 Linux DIG Command Examples for DNS Lookup
http://www.thegeekstuff.com/2012/02/...mand-examples/