DNS

CNAME

Alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name.

How do I find the authoritative NS for a domain?

dig SOA domain.com OR nslookup or dig NS domain.com

A

Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host

AAAA

Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.

What are the server layers in DNS?

"1. Your computer will send the DNS request to your local DNS server 2. This will act as your DNS client on your behalf 3. The Local DNS Server will have a list of Root Name Servers pre-installed. 4. This query contains three fields: example.net IN A domain name (internet) (A record for IP address) 5. The root server returns: Authority section TLD TTL domain name .... Additional Section (GLUE RECORDS) domain name TTL IN A IP ADDRESS .... 6. Now we have a list of TLD servers that can process ____.net. We then contact the IP ADDRESS found in the glue record 7. We have the TLD server address that we send the same query as in 4 8. The TLD Server will then return the next set of servers for ""example.net"" which will also have glue records for the next set of servers 9. Finally, we use the same query for the server in this glue record. 10. The response now contains an ""Answers"" section, which gives us the final IP address associated. 11. Your local DNS server now sends the answer back to your machine. "

How do you query a specific DNS server using dig?

"By default dig uses the DNS servers defined in your /etc/resolv.conf file. If you want to use another DNS server to perform the query, specify in the terminal as @dnsserver. For example, you can specific Google's public DNS using ""dig @8.8.8.8 example.com"""

NS

Delegates a DNS zone to use the given authoritative name servers

Root name server

Directly answers requests for records in the root zone and answers other requests by returning a list of the authoritative name servers for the appropriate top-level domain (TLD).

MX

Maps a domain name to a list of message transfer agents for that domain

TXT

Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data

PTR

Pointer to a canonical name. Unlike a CNAME, DNS processing stops and just the name is returned. The most common use is for implementing reverse DNS lookups

SPF

Sender Policy Framework (SPF) is a simple email validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain is being sent from a host authorized by that domain's administrators.[1] The list of authorized sending hosts for a domain is published in the Domain Name System (DNS) records for that domain in the form of a specially formatted TXT record. Email spam and phishing often use forged sender addresses, so publishing and checking SPF records can be considered anti-spam techniques.

dig example.com ANY

To view all record types. Dig without a flag at the end will default to the A record

What protocol and port are used for DNS?

UDP and Port 53

DNS Resolution

http://royal.pingdom.com/2009/06/08/a-visual-explanation-of-how-dns-lookups-work/