134 dns name resolution version a.01 h3065s module 12 slides

1

DNS Name Resolution

Version A.01H3065S Module 12 Slides

2 © 1999 Hewlett-Packard Co.

H3065S A.01

Resolving Host Names to IP Addresses

a673123

BIND

Resolvinghost names to IP

addresses NIS/NIS+hosts Map/etc/hosts


H3065S A.01

DNS Overview

a673124

HierarchicalName Space

Components

of

DNS

ResolversNameServers


H3065S A.01

The DNS Hierarchical Name Space

a673125

.

govedu

domain host

" root "

com

cail ny

chicago

peoria

rockford

sanfran

oakland

la

nyc

albany

buffalo

Legend:

ibmacme hp


H3065S A.01

• Private name space is not connected to the public internet.• Organizations/companies can manage namespace as desired.

Public and Private Name Spaces

a69810

.

govedu com

cail ny

chicago

peoria

rockford

sanfran

oakland

la

nyc

albany

buffalo

ibmacme hp

.

com

gail ny

chicago

peoria

rockford

atlanta

athens

macon

nyc

albany

buffalo

hp

Public Name Space Private Name Space• Public Name space is connected to the public internet.• Organizations/companies are delegated responsibility for names/IPs within their domains.


H3065S A.01

in-addr.arpa Name Space

a69811

0

.

arpa

1281 254

in-addr

21 3

10 255

2551

sanfran oakland la

. . . . . .

. . . . . .

com

hp

ca

oakland lasanfran

128.1.1.1 128.1.1.2 128.1.1.3. . .. . .

sanfran.ca.hp.com = 1.1.1.128.in-addr.arpa.


H3065S A.01

Name Servers

a673128

ca.hp.com name server

sanfran.ca.hp.com 128.1.1.1oakland.ca.hp.com 128.1.1.2la.ca.hp.com 128.1.1.3

A DNS name server• resolves IP addresses to host names for clients• is delegated authority over a portion of the name space• can delegate authority to other name servers• should have a secondary name server as a backup

Example


H3065S A.01

Name Server Zones

a673129

. . . . . . . . .

hp

com .. .

corp ca az il ga wa ny tx nc

.hp.com Zone

hp.com domain

Delegated Subdomains

edu gov

.


H3065S A.01

Resolving Host Names in the Local Domain

a673130

oakland.ca.hp.com ca.hp.com NS

sanfran 128.1.1.1oakland 128.1.1.2la 128.1.1.3

# telnet la.ca.hp.com

la.ca.hp.com?

la = 128.1.1.3


H3065S A.01

Resolving Host Names in Other Domains

a69812

oakland# telnet atlanta.ga.hp.com

oakland ca.hp.com NS

. NS

com. NS

hp.com. NS

ga.hp.com. NS

atlanta.ga.hp.com?go to com. NS!

atlanta.ga.hp.com?

go to hp.com. NS!

atlanta.ga.hp.com?

go to ga.hp.com. NS!

atlanta.ga.hp.com?

atlanta = 128.1.3.1

atlanta.ga.hp.com?

128.1.3.1


H3065S A.01

Configuring a Primary Name Server

a673132

Notify the internic of your new subdomain.Fully qualify host names in /etc/hosts.Create a directory for the DNS database files.Create a parameter file for hosts_to_named.Create the DNS data and boot files with hosts_to_named.Download a db.cache file with pointers to the root servers.Modify /etc/rc.config.d/namesvrs and start the named daemon.Configure DNS client functionality on the primary server.

1.2.3.4.5.6.7.8.


H3065S A.01

Configuring a Secondary Name Server

a673133

Create a directory for the DNS data files.FTP a boot configuration file from the primary. FTP a copy of db.127.0.0 and db.cache from the primary.FTP additional DNS data files from the primary (optional).Modify /etc/rc.config.d/namesvrs and start named.Configure DNS client functionality on the secondary server.

1.2.3.4.5.6.


H3065S A.01

Configuring DNS Clients

a673134

1. Create /etc/resolv.confsearch ca.hp.com hp.comnameserver 128.1.1.1nameserver 128.1.1.2

2. Modify /etc/nsswitch.confhosts: dns nis files

3. Modify /etc/hosts127.0.0.1 localhost128.1.1.3 la.ca.hp.com la

4. Modify ~/.rhosts, /etc/hosts.equiv, and other files la user1

la.ca.hp.com. user1


H3065S A.01

Configuring the Name Service Switch

a673135

Q: Where should I look up host names? DNS? /etc/hosts? NIS?

hosts: files

hosts: dns nis files

hosts: files [NOTFOUND=continue] dns

hosts: files [NOTFOUND=continue] nis

A: Check /etc/nsswitch.conf!

ororor


H3065S A.01

Testing DNS with nslookup

a673136

Name Server: sanfran.ca.hp.comAddress: 128.1.1.1

Trying DNSName: oakland.ca.hp.comAddress: 128.1.1.2

# nslookup> server 128.1.1.1 # Choose a name server> oakland.ca.hp.com # Resolve a hostname to an IP> 128.1.1.2 # Resolve an IP to a hostname> exit


H3065S A.01

DNS Boot and Data Files

a673137

/etc/named.data

db.cache

db.ca

db.127.0.0

db.128.1.1

; Define the DNS data directory

directory /etc/named.data

; Define which domains this name server ; can serve, and which file contains the ; records for each of those domains. Note ; this name server is primary for all ; of the domains listed here.

primary ca.hp.com db.caprimary 1.1.128.in-addr.arpa db.128.1.1primary 0.0.127.in-addr.arpa db.127.0.0cache . db.cache

/etc/named.boot on the primary ca.hp.com name server:


H3065S A.01

Loading the DNS Data Files

a673138

System boot initiated

named starts at run level 2

named decides which db files to load

named loads db files in cache

Ready to resolve host names!

/etc/rc.config.d/namesvrs

/etc/named.boot

/etc/named.data/db.*


H3065S A.01

Updating the Primary Server

a673139

1. Update /etc/hosts on the primary.# vi /etc/hosts

2. Rebuild DNS data files with hosts_to_named.# cd /etc/named.data# hosts_to_named -f param

3. Reload DNS data files in cache with sig_named restart.# sig_named restart


H3065S A.01

Updating the Secondary Server

a673140

ca.hp.com. IN SOA sanfran.ca.hp.com root.sanfran.ca.hp.com (

3600 ; Retry every 1 hour

604800 ; Expire after 1 week

86400 ) ; Minimum TTL of 1 day

1 ; Serial10800 ; Refresh every 3 hours

Q: How do I know if my DNS data files are up to date? Q: When should I refresh my DNS data files?

Secondary Name Server named Daemon

A: named consults a data file’s SOA record to determines if/when the file must be updated:

134 dns name resolution version a.01 h3065s module 12 slides

Documents