Chapter 3 Flashcards
A (Address) record
A type of DNS data record that maps the IPv4 address of an Internet-connected device to its domain name.
AAAA (Address) record
A type of DNS data record that maps the IPv6 address of an Internet-connected device to its domain name. Pronounced “quad-A record.”
address translation
A technique in which IP addresses used on a private network are assigned a public IP address by a gateway when accessing a public network.
anycast address
A type of IPv6 address that represents a group of interfaces, any one of which (and usually the first available of which) can accept a transmission. At this time, anycast addresses are not designed to be assigned to hosts, such as servers or workstations, but rather to routers.
APIPA (Automatic Private IP Addressing)
A service available on Windows computers that automatically assigns the computer’s NIC a link-local IPv4 address in the range of 169.254.0.1 through 169.254.255.254.
authoritative server
The authority on computer names and their IP addresses for computers in their domains.
broadcast
A message that is read by every node on a network.
broadcast domain
Logically grouped network nodes that can communicate directly via broadcast transmissions. By default, switches and repeating devices, such as hubs, extend broadcast domains. Routers and other Layer 3 devices separate broadcast domains.
caching DNS server
A server that accesses public DNS data and caches the DNS information it collects.
canonical name
The true name of a server, such as www.example.com, as opposed to one of many alias names a server might have, such as ns1.example.com.
classful addressing
An IP addressing convention that adheres to network class distinctions, in which the first 8 bits of a Class A address, the first 16 bits of a Class B address, and the first 24 bits of a Class C address are used for network information.
CLI (command-line interface)
A graphic-free user interface, such as the Command Prompt application in Windows, where technicians can enter commands more quickly and with more flexibility than in a GUI (graphical user interface) environment.
CNAME (Canonical Name) record
A type of DNS data record that holds alternative names for a host.
default gateway
The gateway device that nodes on the network turn to first for access to the outside world.
device ID
See extension identifier.
DHCP (Dynamic Host Configuration Protocol)
An Application layer protocol in the TCP/IP suite that manages the dynamic distribution of IP addresses on a network.
DHCP pool
The predefined range of addresses that can be leased to any network device on a particular segment.
DHCP reservation
An IP address that is set aside by a DHCP server for a specific network client, which is identified by its MAC address.
DHCP scope
A shortage of available IP addresses on a network so that no new clients can connect to the network.
DHCPv6
The version of DHCP used with IPv6.
dig (domain information groper)
A utility available on Linux and macOS that provides more detailed domain information than nslookup. Use dig to query DNS nameservers for information about host addresses and other DNS records.
DKIM (DomainKeys Identified Mail)
An authentication method that uses encryption to verify the domain name of an email’s sender.
DMZ (demilitarized zone)
An area on the perimeter of a network that is surrounded by two firewalls—an external firewall that is more porous to allow more types of access, and an internal firewall that is more hardened to provide greater protection to the internal network.
DNAT (Destination Network Address Translation)
A type of address translation in which a gateway has a pool of public IP addresses that it is free to assign to a local host whenever the local host makes a request to access the Internet.
DNS (Domain Name System or Domain Name Service)
A hierarchical way of tracking domain names and their addresses, devised in the mid-1980s.
domain name
The last two parts of an FQDN, such as mycompany.com. Usually, a domain name is associated with the company’s name and its type of organization, such as a university or military unit.
DNS zone
A portion of the DNS namespace for which one organization is assigned authority to manage.
dual stacked
A type of network that supports both IPv4 and IPv6 traffic.
dynamic IP address
An IP address that is assigned to a device upon request and may change when the DHCP lease expires or is terminated.
elevated Command Prompt
A Command Prompt window with administrative privileges.
EUI-64 (Extended Unique Identifier-64)
The IEEE standard defining 64-bit physical addresses. In the EUI-64 scheme, the OUI portion of an address is 24 bits in length. A 40-bit extension identifier makes up the rest of the physical address, for a total of 64 bits.
exhausted DHCP scope
A shortage of available IP addresses on a network so that no new clients can connect to the network.
extension identifier
A unique set of characters assigned to each NIC by its manufacturer.
firewall
A device (either a router, a dedicated device, or a computer running special software) that selectively filters or blocks traffic between networks.
forward zone
A DNS lookup file that holds A records.
forwarding DNS server
An optional server that receives queries from local clients but doesn’t work to resolve the queries.
FQDN (fully qualified domain name)
A host name plus domain name that uniquely identifies a computer or location on a network.
gateway
A computer, router, or other device that a host uses to access another network. Gateways perform connectivity, session management, and data translation, so they must operate at multiple layers of the OSI model.
global address
An IPv6 address that can be routed on the Internet. These addresses are similar to public IPv4 addresses. Most global addresses begin with the prefix 2000::/3, although other prefixes are being released.
H.323
A signaling protocol used to make a connection between hosts prior to communicating multimedia data. H.323 has largely been replaced by SIP, which is easier to use.
host ID
The portion of an IP address that identifies the host on a network.
host name
The first part of an FQDN, such as www or ftp, which identifies the individual computer on the network.
IANA (Internet Assigned Numbers Authority)
A nonprofit, U.S. government-funded group that was established at the University of Southern California and charged with managing IP address allocation and the Domain Name System. The oversight for many of IANA’s functions was given to ICANN in 1998; however, IANA continues to perform Internet addressing and Domain Name System administration.
ICANN (Internet Corporation for Assigned Names and Numbers)
The nonprofit corporation currently designated by the U.S. government to maintain and assign IP addresses.
ICMP (Internet Control Message Protocol)
A core protocol in the TCP/IP suite that notifies the sender when something has gone wrong in the transmission process and packets were not delivered.
ICMPv6
The version of ICMP used with IPv6 networks. ICMPv6 performs the functions that ICMP, IGMP, and ARP perform in IPv4. It detects and reports data transmission errors, discovers other nodes on a network, and manages multicasting.
ifconfig
An interface configuration and management utility used with UNIX and Linux systems.
interface
A network connection made by a node or host on a network.
interface ID
The last 64 bits, or four blocks, of an IPv6 address that uniquely identify the interface on the local link.
IP exclusion
One or more IP addresses used for static IP assignments and excluded from the IP address pool so the server doesn’t offer those IP addresses to other clients.
IP reservation
An IP address that is set aside by a DHCP server for a specific network client, which is identified by its MAC address.
IPAM (IP address management)
A standalone product or application embedded in another product, such as Windows Server, that provides a way to plan, deploy, and monitor a network’s IP address space.
ipconfig
The utility used to display and alter TCP/IP addressing and domain name information in the Windows client operating systems.
IPv4 (Internet Protocol version 4)
The Internet Protocol standard released in the 1980s and still commonly used on modern networks. It specifies 32-bit addresses composed of four octets.
IPv6 (Internet Protocol version 6)
A standard for IP addressing that is gradually replacing the current IPv4. Most notably, IPv6 uses a newer, more efficient header in its packets and allows for 128-bit source and destination IP addresses, which are usually written as eight blocks of hexadecimal numbers, such as 2001:0DB8:0B80:0000:0000:00D3:9C5A:00CC
iterative query
A DNS query that does not demand a resolution, which means the server provides the information only if it already has that information available.
LDAP (Lightweight Directory Access Protocol)
A standard protocol for accessing network directories.
LDAPS (Lightweight Directory Access Protocol over SSL)
A version of LDAP that uses SSL to encrypt its communications with network directories and clients.
lease time
A time limit on the validity of a DHCP-issued IP address.
link
Any LAN (local area network) bounded by routers.
link local address
An IP address that is automatically assigned by an operating system to allow a node to communicate over its local subnet if a routable IP address is not available.
local link
Any LAN (local area network) bounded by routers.
loopback address
An IP address reserved for communicating from a node to itself, used mostly for troubleshooting purposes.
MAC reservation
An IP address that is set aside by a DHCP server for a specific network client, which is identified by its MAC address.
MX (Mail Exchanger) record
A type of DNS data record that identifies a mail server and that is used for email traffic.
multicast
Transmissions in which one host sends messages to multiple hosts.
multicast address
A type of IPv6 address that represents multiple interfaces, often on multiple nodes.
name resolution
The process of discovering the IP address of a host when the FQDN is known.
NAT (Network Address Translation)
A technique in which IP addresses used on a private network are assigned a public IP address by a gateway when accessing a public network.
neighbors
Two or more nodes on the same link.
netmask
In IPv4 addressing, a 32-bit number that helps one computer find another by indicating what portion of an IP address is the network portion and what portion is the host portion.
network ID
The portion of an IP address common to all nodes on the same network or subnet.
node ID
The portion of an IP address that identifies the node on a network.
NS (Name Server) record
A DNS lookup file that indicates the authoritative name server for a domain. It’s mostly used for delegating subdomains to other name servers.
nslookup (name space lookup)
A TCP/IP utility that allows a technician to query the DNS database from any computer on the network and find the host name of a network node by specifying its IP address, or vice versa. This ability is useful for verifying that a host is configured correctly and for troubleshooting DNS resolution problems.
NTP (Network Time Protocol)
A simple Application layer protocol in the TCP/IP suite used to synchronize the clocks of computers on a network. NTP depends on UDP for Transport layer services.
octet
One of 4 bytes that are separated by periods and together make up an IPv4 address.
open source
Software whose code is publicly available for use and modification.
OUI (Organizationally Unique Identifier)
A 24-bit character sequence assigned by IEEE that appears at the beginning of a network interface’s physical address and identifies the NIC’s manufacturer.
PAT (Port Address Translation)
A form of address translation that assigns a separate TCP port to each ongoing conversation, or session, between a local host and an Internet host.
ping (Packet Internet Groper)
A TCP/IP troubleshooting utility that can verify TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. Ping uses ICMP to send echo request and echo reply messages.
primary DNS server
The authoritative name server for an organization, which holds the authoritative DNS database for the organization’s zones. This server is contacted by clients, both local and over the Internet, to resolve DNS queries for the organization’s domains.
private IP address
IP addresses that can be used on a private network but not on the Internet. IEEE recommends the following IP address ranges for private use: 10.0.0.0 through 10.255.255.255; 172.16.0.0 through 172.31.255.255; and 192.168.0.0 through 192.168.255.255.
process
An instance of running a computer application or service.
PTR (Pointer) record
A type of DNS data record that is used for reverse lookups, to provide a host name when the IP address is known.
public IP address
An IP address that is valid for use on public networks, such as the Internet.
RA (router advertisement)
A message from a router in response to a client’s solicitation and provides DHCP information.
recursive query
A DNS query that demands a resolution or the response that the information can’t be found.
registered port
The TCP/IP ports in the range of 1024 to 49,151. These ports can be used by network users and processes that are not considered standard processes. Default assignments of these ports must be registered with IANA.
resource record
The element of a DNS database stored on a name server that contains information about TCP/IP host names and their addresses.
reverse zone
A DNS lookup file that holds A records where the IP addresses must be stored in reverse— with the last octet listed first—plus the domain .in-addr.arpa. For example, the IP address 1.2.3.4 would be stored in a PTR record as 4.3.2.1.in-addr.arpa.
root server
A DNS server maintained by ICANN and IANA that is an authority on how to contact the top-level domains, such as those ending with .com, .edu, .net, .us, and so on. ICANN oversees the operation of 13 clusters of root servers around the world.
RS (router solicitation)
A message from a client to a router requesting network configuration information.
scope options
Specific configuration information, such as a time limit and a default gateway IP address, that is shared from a DHCP server along with an IP address assignment.
secondary DNS server
The backup authoritative name server for an organization.
session
An ongoing conversation between two hosts.
SIP (Session Initiation Protocol)
A signaling protocol that is used to make an initial connection between hosts but that does not participate in data transfer during the session.
SMB (Server Message Block)
A protocol for communications and resource access between systems, such as clients and servers.
SNAT (Static Network Address Translation or Source Network Address Translation)
A type of address translation in which a gateway assigns the same public IP address to a host each time it makes a request to access the Internet.
SPF (Sender Policy Framework)
A validation system that helps fight spam by identifying the email servers allowed to send email on behalf of a domain.
socket
A logical address consisting of a host’s IP address and the port of an application running on the host with a colon separating the two values.
SRV (Service) record
A type of DNS data record that identifies the hostname and port of a computer hosting a specific network service besides email, such as FTP or SIP.
static IP address
An IP address that is manually assigned to a device and remains constant until it is manually changed.
subnet
A smaller network within a larger network in which all nodes share a network addressing component and a fixed amount of bandwidth.
subnet ID
The 16 bits, or one block, in an IPv6 address that can be used to identify a subnet on a large corporate network.
subnet mask
In IPv4 addressing, a 32-bit number that helps one computer find another by indicating what portion of an IP address is the network and subnet portion and what portion is the host portion.
TFTP (Trivial File Transfer Protocol)
A TCP/IP Application layer protocol that is seldom used by humans. Computers commonly use it as they are booting up to request configuration files from another computer on the local network. Unlike FTP, TFTP relies on UDP at the Transport layer using port 69.
TLD (top-level domain)
The last part of an FQDN and the highest-level category used to distinguish domain names—for example, .org, .com, and .net. A TLD is also known as the domain suffix.
TTL (Time to Live)
A field that indicates the maximum duration that an IPv4 packet can remain on the network before it is discarded. Although this field was originally meant to represent units of time, on modern networks it represents the number of times a packet can still be forwarded by a router, or the maximum number of router hops remaining.
TXT (Text) record
A type of DNS data record that holds any type of free-form text. It might contain text designed to be read by humans regarding network, server, or accounting issues.
tunneling
The process of encapsulating one type of protocol in another. Tunneling is the way in which higher-layer data is transported over VPNs by Layer 2 protocols.
unicast address
A type of IPv6 address that represents a single node on a network.
well-known port
The TCP/IP ports numbered 0 to 1023, so named because they were long ago assigned by Internet authorities to popular services and are, therefore, well known and frequently used.
WSL (Windows Subsystem for Linux)
A Linux shell CLI in Windows that allows users to interact with underlying Windows functions and system files.
