DNS RECORDS Flashcards
Start of Authority (SOA):
This is a record of information containing data
on DNS zones and other DNS records. A DNS zone is the part of a
domain for which an individual DNS server is responsible. Each zone
contains a single SOA record.
Name Server (NS):
record stores information that identifies the name servers in the domain that store information for that domain.
Service Locator (SRV):
This is a generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.
Canonical Name (CNAME):
This record stores additional hostnames, oraliases, for hosts in the domain. CNAME records give a single computer multiple names
(aliases).
Pointer (PTR):
This record is a pointer to the canonical name, which is
used to perform a reverse DNS lookup, in which case the name is returned when the query originates with an IP address.
IPv4 Address (A):
This record stores information for IPv4 (32-bit) addresses. It is most commonly used to map hostnames to an IP address for a host.
Text (TXT):
This field was originally created to carry human-readable text
in a DNS record, but that purpose has long since passed. Today, it is more common that it holds machine-readable data, such as SPF (Sender PolicyFramework) and DKIM (DomainKeys Identified Mail).
Mail Exchange (MX):
This record stores information about where mail for the domain should be delivered.
packet switching,
messages are broken into smaller pieces called packets.
Each packet is assigned source, destination, and intermediate node addresses.Packets are required to have this information because they do not always use the
same path or route to get to their intended destination. Referred to as
independent routing,
Circuit Switching
, circuit switching requires a
dedicated physical connection between the sending and receiving devices. The
most commonly used analogy to represent circuit switching is a telephone
conversation in which the parties involved have a dedicated link between them
for the duration of the conversation. When either party disconnects, the circuit is
broken, and the data path is lost.
distance-vector routing
ith distance-vector router communications, each router on the network
communicates all the routes it knows about to the routers to which it is directly
attached. In this way, routers communicate only with their router neighbors and
are unaware of other routers that may be on the network.
The communication between distance-vector routers is known as hops.
RIP:
RIP is a distance-vector routing protocol. RIP
is limited to a maximum of 15 hops. One of the downsides of the protocol
is that the original specification required router updates to be transmitted
every 30 seconds.
RIPv2:
The second version of RIP dealt with the shortcomings of the
original design. Authentication was included to enable secure
transmissions; also, it changed from a network-wide broadcast discovery method to a multicast method to reduce overall network traffic. However,
to maintain compatibility with RIP, RIPv2 still supports a limit of 15 hops
EIGRP:
: This protocol enables routers to exchange information more
efficiently than earlier network protocols. EIGRP uses its neighbors to
help determine routing information. Routers configured to use EIGRP
keep copies of their neighbors’ routing information and query these tables to help find the best possible route for transmissions to follow
Link-State Routing
A router that uses a link-state protocol differs from a router that uses a distancevector protocol because it builds a map of the entire network and then holds that
map in memory. a network that uses a link-state protocol, routers send linkstate advertisements (LSAs) that contain information about the networks to which they connect. The LSAs are sent to every router on the network, thus enabling the routers to build their network maps.
