1. Module 12: Domain Name System (DNS)

2. Overview Domain Name System (DNS) Name Resolution
Configuring the DNS Files
Planning a DNS Implementation

3. Domain Name System (DNS)

4. How DNS Works Name DNS Server Resolver Application Application Sockets
Transport
Transport
Internet
Internet
Network
Network

5. Domain Name Space Countries COM EDU ORG New Zealand (NZ) Seattle
Root-Level Domain
Countries
Top-Level Domain
COM
EDU
ORG
New Zealand (NZ)
Second-Level Domain
Seattle
Student
microsoft
compaq
purdue

6. Zones of Authority com Microsoft MKTG CORP R&D Zone 1 Zone 3 Zone 2
Name
Server
Name
Servers
R&D
Name
Server

7. Name Server Roles Primary Name Server
Zone information in locally maintained files
Secondary Name Server
Zone information downloaded from a master name server
Master Name Server
Source of information for a secondary server; can be a primary or secondary server
Caching Only
Does not keep any zone information

8. Name Resolution 2 3 4 5 6 1 8 7 Local Name Server Root Name Server gov
Iterative
Queries
Root
Name Server 2 3 4
gov
Name Server 5 6 1 8
Recursive
Query 7
whitehouse.gov
Name Server
DNS
Client

9. Inverse Queries Special Domain for Inverse Queries in-addr.arpa
IP Addresses Reversed when Converted to DNS Inverse Queries
becomes query for in-addr.arpa

10. Caching and TTL DNS Servers Cache Iterative Queries
Each Cached Entry Is Given a Time to Live (TTL)
When the TTL Expires, the Entry Is Flushed from the Cache
The Remaining TTL Is Sent to the Resolver in the Recursive Response

11. Configuring the DNS Files
Database File (zone.dns)
Contains resource records for the zone
Typically maps host names to IP addresses
Reverse Lookup File (z.y.w.x.in-addr.arpa)
Maps IP addresses to host names
Cache File (cache.dns)
Names and addresses of root domain name servers
Boot File
Used by manual start-up method

12. The Database File Stores Resource Records RFC 1034 Compliant
SOA, A, NS, PTR, CNAME, MX, HINFO
Microsoft Specific
WINS, WINS-R

13. The Reverse Lookup File
Supports inverse queries
For inverse queries for IP network , file name created:
db in-addr.arpa
Example resource record entry:
in-addr.arpa. IN PTR mailsrv3.microsoft.com.

14. The CACHE File Contains Names and Addresses for Root Domain Servers
Windows NT 4.0 Provides the Cache File for the Internet
Example entry:
IN NS A.ROOT-SERVERS.NET.
A.ROOT-SERVERS.NET A

15. The BOOT File Not RFC-Based, Part of BIND Implementation
Controls Start-up Behavior of BIND-Compliant DNS Server
Microsoft DNS Server Can Be Configured to Use Boot File
Boot File Commands:
Directory
Cache
Primary
Secondary

16. Planning a DNS Implementation
Small Companies 
Can use ISP DNS servers for queries and to store company domain names
Larger Companies
Maintain their own DNS servers
Two DNS Servers Recommended
Primary name server
Secondary name server

17. Registering with the Parent Domain
Second-Level Domain
Contact InterNIC
microsoft.com
compaq.com
purdue.edu
Seattle
Student
Contact Domain Administrator

18. Lab 16: Planning DNS Server Implementation

19. Review Domain Name System (DNS) Name Resolution
Configuring the DNS Files
Planning a DNS Implementation