net + domain 3 network operations

DHCP Snooping

Switch security feature that blocks rogue DHCP servers by validating DHCP messages and distinguishing trusted from untrusted ports.

Rogue DHCP Server

Unauthorized DHCP server that can provide clients with malicious or incorrect network configuration.

DHCP Snooping Binding Table

Table containing legitimate DHCP-learned mappings such as IP address, MAC address, VLAN, lease, and interface.

Trusted DHCP Port

Switch port permitted to receive DHCP server messages; normally faces the legitimate DHCP server or trusted uplink.

Untrusted DHCP Port

Default DHCP snooping state for client-facing ports; DHCP server messages are restricted.

ip dhcp snooping

Cisco IOS command that enables DHCP snooping globally.

ip dhcp snooping vlan

Cisco IOS command that enables DHCP snooping for specified VLANs.

ip dhcp snooping trust

Cisco interface command that marks an interface as trusted for DHCP snooping.

Dynamic ARP Inspection (DAI)

Switch security feature that validates ARP messages to help prevent ARP spoofing and poisoning.

ARP

Address Resolution Protocol; resolves IPv4 addresses to MAC addresses on a local network.

ARP Spoofing

Attack where forged ARP messages associate an IP address with an attacker's MAC address.

ARP Poisoning

Corruption of ARP information using fraudulent IP-to-MAC mappings.

ip arp inspection vlan

Cisco command that enables Dynamic ARP Inspection for specified VLANs.

Running Configuration

Current active configuration on a network device.

Startup Configuration

Saved configuration loaded when a network device boots.

copy running-config startup-config

Cisco IOS command used to save the active configuration.

DNS

Domain Name System; resolves domain and host names using distributed DNS records.

Forward Lookup Zone

DNS zone primarily containing records used to resolve hostnames to address or other DNS information.

Reverse Lookup Zone

DNS zone used to resolve an IP address back to a hostname, typically using PTR records.

CNAME Record

Canonical Name record; maps an alias hostname to another canonical hostname.

A Record

DNS record mapping a hostname to an IPv4 address.

AAAA Record

DNS record mapping a hostname to an IPv6 address.

PTR Record

DNS record used for reverse lookup from an IP address to a hostname.

MX Record

DNS record identifying the mail server responsible for receiving email for a domain.

FQDN

Fully Qualified Domain Name; complete DNS name containing the hostname and full domain hierarchy.

Hostname

Name identifying a particular host or device, such as docs in docs.example.com.

Domain Name

Hierarchical DNS name identifying an administrative namespace, such as example.com.

TLD

Top-Level Domain; highest common level of a domain name, such as .com, .org, or .net.

Alias

Alternate DNS name used to reference another canonical hostname.

IIS

Internet Information Services; Microsoft's web server platform.

Intranet

Private internal network or website intended for members of an organization.

DHCP

Dynamic Host Configuration Protocol; automatically supplies clients with IP configuration.

DHCP Scope

Range of IP addresses and DHCP options configured for clients on a particular subnet.

Address Pool

Set of IP addresses within a DHCP scope that can be leased to clients.

DHCP Lease

Temporary assignment of an IP address and configuration to a DHCP client.

Lease Duration

Amount of time a DHCP client may use its assigned IP address before renewal is required.

Exclusion Range

Addresses inside a DHCP scope that the server is instructed not to lease.

DHCP Reservation

Permanent association of a particular DHCP client with a specific IP address, usually based on MAC address.

DHCP Option

Additional configuration delivered to clients, such as default gateway, DNS server, or domain name.

Default Gateway

Router IP address a host uses to reach destinations outside its local subnet.

DNS Server

Server that answers or processes DNS name-resolution queries.

DHCP Authorization

Approval allowing a DHCP server to provide leases in an Active Directory environment.

Activate Scope

Enables a configured DHCP scope so it can begin leasing addresses.

Subnet

Logical subdivision of an IP network.

Subnet Mask

Value identifying the network and host portions of an IPv4 address.

IPv6

128-bit Internet Protocol addressing system designed as the successor to IPv4.

NDP

Neighbor Discovery Protocol; IPv6 protocol used for neighbor discovery, router discovery, address resolution, and related functions.

DAD

Duplicate Address Detection; IPv6 process that checks whether a tentative address is already being used.

Neighbor Solicitation (NS)

NDP message used to discover neighbors and perform Duplicate Address Detection.

Neighbor Advertisement (NA)

NDP message used to respond to Neighbor Solicitations or announce IPv6 neighbor information.

Router Solicitation (RS)

NDP message sent by a host requesting routers to immediately send Router Advertisements.

Router Advertisement (RA)

NDP message sent by routers containing prefix, gateway, and autoconfiguration information.

SLAAC

Stateless Address Autoconfiguration; allows IPv6 hosts to configure addresses using router advertisements without stateful DHCP.

Port Mirroring

Switch feature that copies traffic from selected ports or VLANs to a monitoring port.

SPAN

Switch Port Analyzer; Cisco implementation/name for port mirroring.

Mirror Source

Interface whose traffic is copied during port mirroring.

Mirror Destination

Interface that receives copied traffic for monitoring.

IDS

Intrusion Detection System; monitors activity for threats and typically alerts rather than directly blocking them.

IPS

Intrusion Prevention System; monitors traffic and can actively block or prevent malicious activity.

Packet Analyzer

Tool used to capture and inspect network packets.

Port Mirroring Overhead

Additional switch and destination-port workload caused by copying network traffic for monitoring.

PHY

Physical layer; OSI Layer 1 dealing with physical media, signaling, connectors, and transmission.

Physical Network Diagram

Diagram showing physical devices, connections, ports, locations, and cabling.

Logical Network Diagram

Diagram showing logical relationships such as subnets, VLANs, routing, and IP addressing.

Color-Coding

Diagram technique using different colors to represent different cable or connection types.

Line Styles

Diagram technique using solid, dashed, or other line patterns to represent different connection types.

IP Address

Logical Layer 3 address identifying an IP interface.

TCP/UDP Port

Layer 4 number identifying an application or service endpoint.

DHCP Scope

Range and configuration used by DHCP for clients on one subnet.

DNS Forwarder

DNS server configuration that sends unresolved client queries to another DNS server.

Forwarding

DNS process of sending a query to another designated DNS server for resolution.

Authoritative DNS Server

DNS server containing official DNS records for a zone for which it is authoritative.

Recursive DNS Resolver

DNS server that obtains a final answer for a client by querying other DNS servers as needed.

Recursive Query

Query requiring the DNS server to return the requested answer or an error.

Root DNS Server

Top-level DNS hierarchy server that directs resolvers toward appropriate TLD name servers.

TLD Name Server

DNS server responsible for directing queries for a top-level domain toward authoritative servers.

DNS Propagation

Common term for the period during which cached DNS data across resolvers may still reflect old records after a change.

DNS Cache

Temporarily stored DNS query results used to speed future lookups.

TTL

Time to Live; DNS value controlling how long a resolver may cache a record before refreshing it.

HOSTS File

Local file containing static hostname-to-IP mappings that can override normal DNS lookup behavior.

Firewall

Security control that permits or blocks network traffic according to configured rules.

SSL Certificate

Common term for a digital certificate used with TLS to authenticate a website or service.

Jump Box

Hardened intermediary system used to access and administer systems inside a protected network.

Jump Server

Another term for a jump box.

Bastion Host

Hardened system exposed or positioned to provide controlled access to protected resources.

Programmatic Access

Access performed by software, scripts, automation, or APIs rather than interactive human login.

Secret Key

Confidential credential used by applications or automation for authentication; must be securely protected.

Root Account

Highly privileged Unix/Linux administrative account with extensive system permissions.

Least Privilege

Security principle granting only the permissions necessary to perform a required task.

Ordinary Account Credentials

Normal username/password credentials intended for interactive users rather than dedicated automation.

Credential Exposure

Accidental or intentional disclosure of passwords, secret keys, tokens, or other authentication material.

MTU

Maximum Transmission Unit; largest IP packet size that can be transmitted over a link without fragmentation.

Fragmentation

Process of breaking an IP packet into smaller fragments to accommodate a smaller MTU.

IPv4 Identification Field

IPv4 header field used to identify fragments belonging to the same original packet.

Fragment Offset

IPv4 header field identifying where a fragment belongs within the original packet.

MF Flag

More Fragments flag; indicates that additional IPv4 fragments follow.

Sequence Number

TCP field used to track byte ordering and support reliable reassembly of a TCP data stream.

Checksum

Value used to detect accidental corruption or errors in transmitted data.

Header

Control information placed before protocol data, containing fields needed to process the packet or segment.

Options

Optional additional fields that can provide extra protocol functionality.