NETWORK+ GUIDE TO NETWORKS CHAPTER 3
subnet
A smaller network within a larger network in which all nodes share a network addressing component and a fixed amount of bandwidth.
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.
LDAP (Lightweight Directory Access Protocol)
A standard protocol for accessing network-based directories.
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.
lease time
A time limit on the validity of a DHCP-issued IP address.
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.
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.
dual stacked
A type of network that supports both IPv4 and IPv6 traffic.
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.
Network layer IP address
An IP address is assigned to nearly every interface, which is a network connection made by a node on a network. An IP address can be used to find any computer in the world if the IP address is public on the Internet. Applications such as browsers can store and retrieve IP addresses. But for routing purposes, an IP address is used only at the Network layer.
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.
static IP address
An IP address that is manually assigned to a device and remains constant until it is manually changed.
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.
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.
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.
public IP addresses
An IP address that is valid for use on public networks, such as the Internet.
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.
DKIM (DomainKeys Identified Mail)
An authentication method that uses encryption to verify the domain name of an email's sender.
process
An instance of running a computer application or service.
session
An ongoing conversation between two hosts.
forwarding DNS server
An optional server that receives queries from local clients but doesn't work to resolve the queries. Typically, a forwarding server will maintain its own DNS cache from previous queries, and so it might already have the information the client needs. If not, the forwarding server forwards the query to another server to resolve. Several forwarding servers might be strategically placed throughout the organization's network to reduce network traffic on slow links.
H.323
Another 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.
local link or link
Any LAN (local area network) bounded by routers.
global address
Can be routed on the Internet and is similar to public IPv4 addresses. Most begin with the prefix 2000::/3, although other prefixes are being released. The /3 indicates that the first three bits are fixed and are always 001
link local address
Can be used for communicating with nodes in the same link, and is similar to an autoconfigured APIPA address in IPv4. It begins with FE80::/10. The first 10 bits of the reserved prefix are fixed (1111 1110 10), and the remaining 54 bits in the 64-bit prefix are all zeroes.
multicast address
Delivers packets to all nodes in the targeted, multicast group.
well-known ports
Range from 0 to 1023 and are assigned by IANA to widely used and well-known utilities and applications, such as Telnet, FTP, and HTTP.
registered ports
Range from 1024 to 49151 and can be used temporarily by processes for nonstandard assignments for increased security. Default assignments of these registered ports must be registered with IANA
DNS server
Servers that are responsible for tracking computer names and their IP addresses
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.
unicast address
Specifies a single node on a network
A (Address) record
Stores the name-to-address mapping for a host. This resource record provides the primary function of DNS—to match host names to IP addresses, using IPv4 addresses.
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.
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.
primary DNS server
The authoritative name server for the 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.
authoritative server
The authority on computer names and their IP addresses for computers in their domains.
secondary DNS server
The backup authoritative name server for the organization. When a secondary DNS server needs to update its database, it makes the request to the primary server for the update; this process is called a zone transfer.
OUI (Organizationally Unique Identifier)
The first 24 bits (six hex characters) identifies the NIC's manufacturer.
interface ID
The last 64 bits, or four blocks, of an IPv6 address that uniquely identify the interface on the local link.
TLD (top-level domain)
The last part of an FQDN
IANA (Internet Assigned Numbers Authority)
The organization responsible for tracking the assignments of IP addresses, port numbers, and domain names
network ID
The portion of an IP address common to all nodes on the same network or subnet.
Host ID or node ID
The portion of an IP address that identifies the host on a network.
DHCP scope or DHCP protocol
The predefined range of addresses that can be leased to any network device on a particular segment.
name resolution
The process of discovering the IP address of a host when the FQDN is known.
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.
address translation
The process of substituting a private IP address used by computers on a private network with the public IP address of a gateway device or router when these computers need access to other networks or the Internet.
ipconfig
The utility used to display and alter TCP/IP addressing and domain name information in the Windows client operating systems.
DHCPv6
The version of DHCP used with IPv6.,
multicast
Transmissions in which one host sends messages to multiple hosts.
PTR (Pointer) record
Used for reverse lookups, which provide a host name when you know its IP address. PTR records are usually created by ISPs and stored in a specially formatted reverse lookup zone file, or reverse zone. Reverse zones differ from a typical forward lookup zone file, or forward zone, that holds A records, in that the IP addresses must be stored in reverse—with the last octet listed first—plus the domain .in-addr.arpa
TTL (Time to Live)
field that identifies how long the record should be saved in a cache on a server. Administrators can set the TTL based on how volatile is the DNS data (in other words, how often the administrator expects the IP addresses to change). TTL information is included in zone transfers.
octets
four decimal numbers
A hexadecimal number (also called a hex number)
is a number written in the base-16 number system, which uses the 16 numerals 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.
default gateway
is the gateway device that nodes on the network turn to first for access to the outside world.
DHCP (Dynamic Host Configuration Protocol)
server manages the dynamic distribution of IP addresses to devices on a network.
domain name
the last two parts of a host's name (for example, mycompany.com) are called
LDAPS (Lightweight Directory Access Protocol over SSL)
uses SSL to encrypt its communications
AAAA (Address) record
(called a "quad-A record")—Holds the name-to-address mapping for IPv6 addresses
elevated Command Prompt
A Command Prompt window with administrative privileges.
root servers
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.
WSL (Windows Subsystem for Linux)
A Linux shell CLI in Windows that allows users to interact with underlying Windows functions and system files.
Data Link layer MAC address
A MAC address is embedded on every NIC on the globe and is assumed to be unique to that NIC. A MAC address is 48 bits, written as six hex numbers separated by colons, as in 00:60:8C:00:54:99. Nodes on a LAN find each other using their MAC addresses.
gateway
A computer, router, or other device that a host uses to access another network
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.
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.
DNS (Domain Name System or Domain Name Service)
A hierarchical way of tracking domain names and their addresses, devised in the mid-1980s.
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.
RS (router solicitation)
A message from a client to a router requesting network configuration information.
RA (router advertisement)
A message from a router in response to a client's solicitation and provides DHCP information.
broadcast
A message that is read by every node on a network.
A binary number
A number composed of just 0s and 1s, also known as a base-2 number.
Transport layer ports
A port is a number used by the Transport layer to find an application. It identifies one application among several that might be running on a host. For example, a web server application is usually configured to listen for incoming requests at port 80.
DNS zone
A portion of the DNS namespace for which one organization is assigned authority to manage.
recursive query
A query that demands a resolution or the answer "It can't be found." For example, the initial request the resolver makes to the local server is a recursive query. The local server must provide the information requested by the resolver, as in "The buck stops here."
iterative query
A query that does not demand resolution. For example, when the local server issues queries to other servers, the other servers only provide information if they have it.
caching DNS server
A server that accesses public DNS data and caches the DNS information it collects. This server receives DNS queries from local network clients and works to resolve them by contacting other DNS servers for information. Caching DNS servers do not store zone files (which is why they must rely on their caches and resolution efforts), and therefore do not participate in zone transfers, which further helps to reduce network traffic on the intranet.
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.
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. After SIP establishes the connection, other protocols kick in—for example, RTP (Real-time Transport Protocol or Real-time Protocol) that transports streaming audio and video data for VoIP calls.
NTP (Network Time Protocol)
A simple protocol used to synchronize clocks on computers throughout a network. The genius of NTP is how it can almost completely account for the variable delays across a network, even on the open Internet. Not every network has its own time server, but those that do can maintain accuracy to within a millisecond of each other and are closely synced to the UTC (Coordinated Universal Time).
Application layer FQDNs, computer names, and host names
Every host on a network is assigned a unique character-based name called the FQDN (fully qualified domain name),
SMB (Server Message Block)
First used by earlier Windows OSes for file sharing on a network. UNIX uses a version of SMB in its Samba software, which can share files with other operating systems, including Windows systems.
CNAME (Canonical Name) record
Holds alternative names for a host. These names can be used in place of the canonical name, which is the complete and properly formatted name
TXT (Text) record
Holds any type of free-form text. It might contain text designed to be read by humans regarding network, server, or accounting issues
private IP addresses
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.
MX (Mail Exchanger) record
Identifies an email server and is used for email traffic.
anycast address
Identifies multiple destinations, with packets delivered to the closest destination.
SRV (Service) record
Identifies the hostname and port of a computer that hosts a specific network service besides email, such as FTP or SIP.
NS (Name Server) record
Indicates the authoritative name server for a domain. It's mostly used for delegating subdomains to other name servers.
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.
extension identifier or device ID
Made up of the last 24-bits and identify the device itself. Manufacturers assign each NIC a unique extension identifier, based on the NIC's model and manufacture date, so that, in theory, no two NICs share the same MAC address.
TFTP (Trivial File Transfer Protocol)
Most commonly used by computers (without user intervention) as they are booting up to request configuration files from another computer on the local network. TFTP uses UDP, whereas normal FTP uses TCP.
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.
subnet mask—Also called a netmask
a 32-bit number that helps one computer find another. The 32 bits are used to indicate what portion of an IP address is the network portion, called the network ID or network address, and what part is the host portion, called the host ID or node ID. Using this information, a computer can determine if another computer with a given IP address is on its own or a different network.
A DHCP (Dynamic Host Configuration Protocol)
a server that manages the dynamic distribution of IP addresses to devices on a network.
IPv6 (Internet Protocol version 6)
addresses have 128 bits and are written as eight blocks of hexadecimal numbers, for example, 2001:0DB8:0B80:0000:0000:00D3:9C5A:00CC Each block contains 16 bits
IPv4 (Internet Protocol version 4)
addresses have 32 bits and are written as four decimal numbers called octets, for example, 92.106.50.200. Each octet, when written in binary, consists of exactly 8 bits. For example, the octet 92 can be written as 0101 1100.