DNS

Question 1

Forward lookup is …

Answer 1

is a dns query sent to external dns servers for resolution of a name into a ip address.

Question 2

Reverse lookup is …

Answer 2

is a dns query sent to an external dns server for resolution of an IP address into a name.

Question 3

Name 3 types of DNS Records and what they are used for. Also explain TTL of a DNS record.

Answer 3

1. A Canonical Name or CNAME record is a type of DNS record that maps an alias name to a true or canonical domain name.

EX. if you have a server where you keep all of your documents online, it might normally be accessed through docs.example.com. You may also want to access it through documents.example.com. One way to make this possible is to add a CNAME record that points documents.example.com to docs.example.com.

2. MX records: MX stands for Mail eXchange. MX Records tell email delivery agents where they should deliver your email.

If our organization receives email directly then our MX record would point to a public IP address for your firewall or internet-facing email server (eg Edge Transport server).

If we use a hosted cloud service for email filtering like Barracuda, then our MX record would point to their IP address(s).

3. A or AAAA records: A record is used to find the IP address of a computer connected to the internet from a name. The A in A record stands for Address. For example, to access the DNSimple website you enter www.dnsimple.com. At our name server there is an A record that points to the IP address 208.93.64.253.
4. TTLs are set by an authoritative nameserver for each resource record. TTLs are used for caching purpose. For example, www.dnsknowledge.com TTL value is 86400 seconds, which is 24 hours.

Question 4

What does DNS Stand for?

Answer 4

Domain Name System

Question 5

What is a SRV record?

Answer 5

Used by AD to find a DC

Question 6

What is PTR record?

Answer 6

Point to Record. IP address to name (reverse lookup zone) Used for troubleshooting tools
DHCP Client automatically updae.
ipconfig/registerdns force update otherwise DNS updates automatically.

Question 7

What is a SOA record?

Answer 7

Start of Authority
Primary name server
Email address of administrator
Domain Serial #