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