Network Services/ DNS Records Flashcards
Dynamic Host Configuration Protocol (DHCP)
o Assigns devices with IP addresses and also provides them a subnet mask, default
gateway, and DNS server
o Operates over ports 67 and 68 using UDP
Domain Name System (DNS)
o Converts domain names to IP addresses using a hierarchical and decentralized
system of naming
o Operates over UDP and TCP using port 53
Zone Transfer
Sharing of information between DNS servers about which domain names they
have and their associated IP addresses
Network Time Protocol (NTP)
o Synchronizes clocks between systems communicating over
o a packet-switched, variable-latency data network
o Sent over UDP using port 123
Dynamic Host Configuration Protocol (DHCP) Part 2
o DHCP also help eliminate configuration errors
▪ Each device will automatically get assigned an IP from a scope
● Scope
o A list of valid IP addresses that are available for
assignment or lease to a client computer or endpoint
device on a given subnet
▪ Use a DHCP reservation
▪ DHCP server will acknowledge the IP that is being used
o D-O-R-A process
▪ Discover, Offer, Request and Acknowledge
If a device attempts to use DHCP and fails to receive its configuration, what
should it do?
▪ It is set to use an APIPA address, or automatic private IP address
o DHCP Relay
▪ Any host that forwards DHCP packets between clients and servers
o DHCP is that it operates using the User Datagram Protocol or UDP
o If the DHCP client and server are on different network segments, the router on
the client’s network segment must be configured with an IP helper address for
DHCP to work properly
Domain Name System (DNS) EX
o Used to help your network clients find a website using human-readable
hostnames instead of numeric IP addresses
o Converts names to numbers and numbers to names
▪ Fully Qualified Domain Name (FQDN)
● This is when a domain name is under a top-level provider
● The most common top-level provider:
o .com
o .mil
o .edu
o .org
o .net
Root Level
The highest level in the DNS hierarchy tree and the root name server
answers requests in the root zone
▪ These servers contain the global list of all the top-level domains, such as
.com, .net, .org, .mil, and others
Top-level Domains
▪ Organizational hierarchy
● .com
● .net
● .org
▪ Geographic hierarchy
● .uk for the United Kingdom
● .fr for France
● .it for Italy
Second-level Domains
These domains site directly below the top-level domain
● For example: diontraining.com is a second level domain, and it
sits underneath the top-level domain of .com
Sub-domain
▪ A new server underneath a second-level domain
Host Level
This is the lowest and most detailed level inside of the DNS hierarchy and
refers to a specific machine
A Records
▪ Address Record
▪ Used to link a hostname to an IPv4 address
▪ A records work for IPv4 addresses
▪ AAAA records work for IPv6 addresses
CNAME Record
▪ Canonical Name Record
▪ Used instead of a A record or AAAA record if you want to point a domain
to another domain name or subdomain
MX Record
▪ Mail Exchange Record
▪ Used to direct emails to a mail serve
▪ Used to indicate how email messages should be routed using the Simple
Mail Transfer Protocol, or SMTP, over port 25
▪ Can only be used to point to another domain, not an IP address
SOA Record
▪ Start of Authority Record
▪ Used to store important information about a domain or zone
DNS zone transfer
The process of sending DNS records data from the primary nameserver to
a secondary name server
▪ Uses the TCP protocol to transfer the data to ensure data is successfully
sent by the primary server and received by the second server
PTR Records
▪ Pointer Records
▪ Used to correlate an IP address with a domain name
▪ The opposite of an A record
▪ Always stored under the .arpa (top-level domain)
TXT Record
Text records
▪ Used by domain administrators to add text into the domain name system
or DNS
▪ A place to store machine-readable data
SRV Records
▪ Service Record
▪ Used to specify a host and port for a specific service
▪ Can specify a port along with our IP address
NS Record
▪ Name Server Record
▪ Used to indicate which DNS name server is the authoritative one for a
domain
External DNS
Records created around the domain names we purchase from a central
authority and use on the public internet
DNS Resolver
Also known as a DNS cache located on an individual host
▪ This temporary database remembers the answers it received from the
DNS server
● Recursive Lookup
o DNS server will hunt it down and report back to your
resolver
● Interactive lookup
o DNS resolve will continually query DNS servers until it finds
the one with the IP for the domain
Network Time Protocol (NTP)
o Synchronizes clocks between systems communicating over a packet-switched,
variable-latency data network
o Sent over UDP using port 123
▪ Stratum
▪ Clients
▪ Servers
o NTP can handle a maximum of 15 stratum levels
