Term 121
Crossover cable
A crossover cable is an Ethernet cable with reversed transmit and receive wire pairs, used to directly connect two similar devices without a switch or hub.
Acronym study
Terms 121–150 of 716 CCNA acronyms and key terms. Each entry includes a plain-English definition and a link to the full 800-word glossary page with exam context and practice questions.
Term 121
A crossover cable is an Ethernet cable with reversed transmit and receive wire pairs, used to directly connect two similar devices without a switch or hub.
Term 122
Carrier Sense Multiple Access with Collision Detection is a network protocol used in Ethernet to manage data transmission and handle collisions when two devices send data at the same time.
Term 123
A Certificate Signing Request is a block of encoded data sent to a Certificate Authority to apply for a digital certificate.
Term 124
curl is a command-line tool that lets you transfer data to or from a server using various network protocols, commonly used to test APIs and download files.
Term 125
In scripting and automation, cut is a command-line utility used to extract specific fields or columns from each line of a file or text stream based on a delimiter or character position.
Term 126
A Cyclic Redundancy Check (CRC) is an error-detecting code used to verify that data transmitted over a network or stored on a device has not been corrupted.
Term 127
A Data Center Interconnect is a network connection that links two or more separate data centers together so they can share data, resources, and services as if they were a single facility.
Term 128
A Data Lifecycle Manager is a system or set of policies that automates the movement, protection, retention, and deletion of data from creation to disposal, ensuring compliance and efficient storage usage.
Term 129
A Data VLAN is a virtual local area network configured on a switch to carry user-generated traffic, separating it from management, voice, or other types of network traffic.
Term 130
A DDoS (Distributed Denial-of-Service) attack is a malicious attempt to disrupt normal traffic of a targeted server, service, or network by overwhelming it with a flood of internet traffic from multiple compromised systems.
Term 131
The Dead timer is the period an OSPF router waits to hear from a neighbor before declaring that neighbor as unreachable and removing it from the routing table.
Term 132
A deauthentication attack is a wireless network exploit where an attacker sends fake disconnection frames to force devices off a Wi-Fi network, often used to capture handshake data or disrupt connectivity.
Term 133
Decapsulation is the process in networking where a device removes headers and trailers from a data packet as it travels up the OSI model layers.
Term 134
A Dedicated Interconnect is a direct, private physical connection between your on-premises network and a cloud provider's network, bypassing the public internet for faster, more reliable, and more secure data transfer.
Term 135
A default app is the program that your operating system automatically uses to open a specific type of file or perform a certain task, such as opening a web link or viewing a photo.
Term 136
A default gateway is a network device, typically a router, that acts as the exit point for traffic from a local network to other networks, including the internet.
Term 137
A default route is a catch-all routing entry that tells a network device where to send packets when no specific route matches the destination address.
Term 138
The Default VLAN is VLAN 1 on most Cisco switches and it is the VLAN to which all switch ports belong by default until they are assigned to a different VLAN.
Term 139
In a Spanning Tree Protocol network, a Designated port is the port on a network segment that has the best path to the root bridge and is responsible for forwarding traffic toward the root bridge.
Term 140
A router elected in an OSPF multi-access network to manage link-state updates and reduce routing protocol traffic.
Term 141
Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network settings to devices on a network, so they can communicate without manual configuration.
Term 142
A DHCP pool is a reserved set of IP addresses that a DHCP server can assign to devices on a network automatically when they request a connection.
Term 143
A network device or feature that forwards DHCP broadcast messages between clients and servers on different subnets so that IP address assignment works across multiple network segments without a separate DHCP server on each one.
Term 144
A DHCP server is a network device or service that automatically assigns IP addresses and other network configuration parameters to devices on a network, eliminating the need for manual configuration.
Term 145
DHCP snooping is a network security feature that filters untrusted DHCP messages to prevent rogue DHCP servers from giving out false IP addresses.
Term 146
DHCPv6 is a network protocol that automatically assigns IPv6 addresses and other configuration settings to devices on a network.
Term 147
Diffie-Hellman is a cryptographic protocol that allows two parties to securely exchange a shared secret key over an untrusted network like the internet.
Term 148
A cryptographic technique used to verify the authenticity and integrity of a digital message or document, ensuring it came from the claimed sender and was not altered.
Term 149
Digital Subscriber Line (DSL) is a technology that uses ordinary copper telephone wires to provide high-speed internet access to homes and businesses.
Term 150
The Dijkstra algorithm is a mathematical method used by OSPF to calculate the shortest path between a router and every other router in a network.