DNS

DNS Components

Name server

- authoritive or recursive

Zone file

- how the name server stores info about domain and how to get there

Resource records

- located in zone file

record name

TTL - time in which the record is discarded

class - Namespace of record info, usually IN for internet

type - type of info stored (A, MX, etc.)

Data - can contain IP address or other info depending on type

DNS Process

Local DNS Server (ISP)

- asks root server if unknown

Root servers

- 13 root servers for the internet

- contain info about top level domains (.org .com .net etc.)

Top level domain

- can give ip of server that record is located on

Authoritive DNS server

- final DNS server with info we want (if no others have)

/etc/hosts

- contains host/ip mappings

- local host listed as default

- manage access to hosts (modify firewall rules instead)

- /etc/hosts.deny

- /etc/hosts.allow

/etc/resolv.conf

- DNS name server mappings (often irrelevant)

DNS setup (popular DNS servers)

BIND

- standard for Linux distros

- full featured power and flexibility

DNSmasq

- lightweight and easy to configure

- DHCP & DNS

- for small networks

Power DNS

- full featured

- most flexibilty & options

DNS tools

nslookup

$ nslookup www.google.com

- query name servers to find info on resource records

dig (domain information grouper)

- gather info about DNS name servers

$ dig www.google.com

- gives more info than nslookup