Cisco Certified Support Technician (CCST) Networking flashcards

Port scanning is a technique used to identify open ports and services on a network host. Attackers use it to discover potential entry points and vulnerabilities.

• Identifies open ports and services.
• Often a precursor to other attacks.
• Can be detected by intrusion detection systems.

Memory trick: Reconnaissance is like a spy casing a joint before the big heist.

A security principle, especially in firewalls, where any access or action not explicitly permitted is automatically denied.

• Provides a secure default posture.
• Often the last rule in a firewall's access control list (ACL).
• Ensures only intended traffic is allowed.

Memory trick: Firewall rules are like bouncers at a club: if you're not on the list, you're not getting in.

Public IPv4 addresses are globally unique and routable on the internet, whereas private IPv4 addresses are reserved for internal networks and are not routable on the internet.

• Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
• NAT is required for devices with private IP addresses to access the internet.
• Public IPs are assigned by Regional Internet Registries (RIRs).

Memory trick: Public for the world, private for the home.

Wireless channel interference occurs when multiple wireless devices or access points operate on the same or overlapping frequency channels, causing signals to collide and degrade performance.

• Common in dense wireless environments.
• Leads to slow speeds, dropped connections, and reduced range.
• Mitigated by selecting non-overlapping channels (e.g., 1, 6, 11 for 2.4 GHz).

Memory trick: Interfering Channels Cause Chaotic Connections.

The default UDP port used by an SNMP manager to receive unsolicited alert messages (traps) from SNMP agents on managed devices.

• UDP Port 162 is for receiving traps.
• UDP Port 161 is for sending requests to agents.
• Traps are asynchronous notifications of events.

Memory trick: 161 for Requests, 162 for Traps – order matters!

IaaS is a cloud computing service model that provides virtualized computing resources over the internet, giving users control over operating systems, applications, and data.

• Cloud provider manages hardware, virtualization, storage, and networking.
• Customer manages OS, middleware, applications, and data.
• Offers the most flexibility and control among cloud service models.

Memory trick: IaaS is for Infrastructure, You Still Install Systems.

NTP (Network Time Protocol) primarily uses UDP port 123 for all its communication, enabling devices to synchronize their clocks with a time server or other network devices.

• Uses UDP port 123.
• Essential for time synchronization.
• Critical for logging, security, and distributed applications.

Memory trick: 123 is as easy as ABC for NTP.

An 'A' (Address) record is a fundamental DNS record type that maps a hostname to an IPv4 address.

• Used for forward DNS lookups.
• Essential for resolving domain names to IP addresses.
• One of the most common DNS record types.

Memory trick: DNS records are like a phonebook, and 'A' is for 'Address' (IPv4).

Quality of Service (QoS) refers to technologies that manage network resources to minimize the impact of network congestion. It ensures that critical applications receive the necessary bandwidth and priority for optimal performance by prioritizing specific traffic types.

• Prioritizes critical network traffic (e.g., VoIP, video).
• Reduces latency, jitter, and packet loss.
• Manages bandwidth allocation.
• Implemented on routers, switches, and firewalls.

Memory trick: QoS: 'Quality' for VIP traffic, 'Service' for all.

A virtual switch is a software application that allows communication between virtual machines on the same host, and often between virtual machines and the external physical network.

• Operates like a physical switch but entirely in software within a hypervisor.
• Connects virtual network adapters of VMs to virtual ports.
• Can bridge to a physical NIC to provide external network access.

Memory trick: Virtual Switches Share Seamlessly.

An IEEE standard for wireless local area networks, also known as Wi-Fi 4, that significantly improved upon previous standards by introducing MIMO, channel bonding, and dual-band operation.

• Operates in both 2.4 GHz and 5 GHz frequency bands.
• Introduced MIMO (Multiple-Input, Multiple-Output) technology.
• Theoretical maximum data rate up to 600 Mbps.
• Backward compatible with 802.11a/b/g.

Memory trick: N for New, for Nifty, for Next-level speed.

Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. It blocks redundant paths that could cause broadcast storms and MAC address table corruption, while still allowing for physical redundancy to provide fault tolerance.

• Prevents Layer 2 loops in switched networks.
• Logically blocks redundant paths.
• Ensures a single active path between any two network devices.
• Root bridge, designated ports, root ports, and blocked ports are key concepts.

Memory trick: STP: 'Stop' the loops, 'Protect' the network.

A standard for message logging that allows network devices to send event messages to a centralized logging server.

• Centralizes log collection.
• Supports various log levels (severities).
• Uses UDP port 514 by default.

Memory trick: Syslog: System Logs, Sent Locally Or Globally.

APIPA is a feature in Windows operating systems that automatically assigns an IP address to a client when no DHCP server is available. The assigned IP address is in the 169.254.0.0/16 range.

• Automatically assigns IP addresses when DHCP fails.
• IP addresses are in the 169.254.x.x range.
• Allows communication only within the local subnet.

Memory trick: DHCP Dreams, APIPA Reality for network setup.

An overly short DHCP lease time in a busy network leads to excessive DHCP renewal traffic and increased load on the DHCP server.

• Clients renew more frequently.
• Generates more broadcast traffic.
• Increases DHCP server CPU and memory usage.

Memory trick: Short lease, high demand: everyone's always asking for a new car.

A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It establishes a barrier between a trusted internal network and untrusted external networks (like the internet).

• Filters traffic based on rules (IP, port, protocol).
• Protects internal networks from external threats.
• Can be hardware, software, or cloud-based.
• Key for enforcing security policies.

Memory trick: Firewall: 'F'or 'Filtering' and 'Fortifying' the network.

A network topology where every device is directly connected to every other device, providing multiple paths for data transmission and high fault tolerance.

• Offers maximum redundancy and reliability.
• Complex to implement and expensive due to many cables and ports.
• Often used in critical backbone networks or small, highly resilient environments.

Memory trick: Mesh creates many paths, making it strong.

A star topology is a network arrangement where every node (workstation, server, or peripheral) is connected to a central hub, switch, or computer.

• Centralized management and fault isolation.
• Easy to add new devices without disrupting the network.
• Failure of the central device brings down the entire network.

Memory trick: Stars are Simple and Strong for Small Setups.

A routing table is a data table stored in a router or networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. It is used to direct network packets.

• Contains information about network destinations.
• Used to determine the best path for forwarding IP packets.
• Essential for inter-network communication (routing).
• Can be populated statically or dynamically (via routing protocols).

Memory trick: Routing Table: The router's 'Roadmap' for packets.

A DHCP feature that permanently assigns a specific IP address to a particular network device based on its MAC address.

• Ensures consistent IP assignment.
• Useful for servers, printers, network infrastructure.
• Requires knowledge of the device's MAC address.

Memory trick: A 'Reservation' guarantees your favorite table (IP address).

A QoS mechanism that handles traffic when a network link becomes congested, typically by using queuing algorithms to prioritize certain traffic types.

• Manages traffic flow during peak usage.
• Uses queuing to determine transmission order.
• Examples include FIFO, Weighted Fair Queuing (WFQ), Class-Based Weighted Fair Queuing (CBWFQ).

Memory trick: When there's a jam (congestion), a good manager directs traffic.

The process where an end-user device (client) performs DNS lookups to resolve a domain name into an IP address before initiating a connection to a server.

• DNS resolution is typically done by the client.
• Servers receive connections to their IP, not their domain name.
• Server's DNS logs might be empty if it doesn't initiate outbound lookups.

Memory trick: Client Connects, Server Sees IP, Not Name.

A network device that connects devices within a local area network (LAN) and forwards data frames selectively to the destination port based on MAC addresses.

• Operates at Layer 2 (Data Link Layer) of the OSI model.
• Uses MAC addresses for intelligent forwarding.
• Reduces network congestion by creating separate collision domains for each port.

Memory trick: Switch to connect, not just broadcast.

A forwarding DNS server is configured to send all DNS queries that it cannot resolve from its local cache or authoritative zones to a specific upstream DNS server, known as a forwarder. This is common in enterprise networks for security, performance, and management.

• Sends unresolved queries to a designated upstream server.
• Can improve security by limiting direct external communication.
• Can improve performance by centralizing external lookups.
• Often used in conjunction with recursive functionality.

Memory trick: Forward means sending it on to someone else.

Subnet mask calculation involves determining the number of bits to borrow from the host portion of an IP address to create subnets. This dictates the number of hosts per subnet and the number of available subnets.

• Formula: 2^h - 2 (where h = number of host bits) gives usable hosts.
• CIDR notation (/prefix) indicates the number of network bits.
• Each subnet requires a network address and a broadcast address, which are not usable by hosts.

Memory trick: Host Power: Two to the 'H' minus two, for subnet sanity.

An IPv6 address type that is globally unique and routable across the entire public internet, allowing direct communication from any internet-connected device.

• Starts with binary 001 (e.g., typically 2000::/3 prefix).
• Equivalent to a public IPv4 address.
• Assigned by Regional Internet Registries (RIRs).

Memory trick: Global for the world, local for the neighborhood.

The 'Emergency' (0) severity level in Syslog indicates that the system is completely unusable. These are critical events that usually result in a crash or a complete failure of a core system component, demanding immediate intervention.

• Highest Syslog severity level (0).
• System unusable, immediate action required.
• Indicates catastrophic failure.

Memory trick: 0 is 'Oh no!', 7 is 'So what?'

The practice of duplicating network components, paths, or functions to ensure that network services remain available even if one or more components fail.

• Achieved through redundant links, devices, power supplies, etc.
• Increases fault tolerance and high availability.
• Can involve protocols like Spanning Tree Protocol (STP) or Hot Standby Router Protocol (HSRP).

Memory trick: Redundancy is your backup plan for uptime.

DNS Caching stores resolved domain names and their IP addresses on a local DNS server to speed up future queries. The Time-to-Live (TTL) value specifies how long these cached entries are considered valid.

• Improves DNS query performance.
• Reduces load on authoritative DNS servers.
• TTL impacts cache freshness and consistency.

Memory trick: Caching is like a speed-dial, and TTL is how long that number stays on the list.

A method used to automatically generate an IPv6 interface identifier (the last 64 bits of an IPv6 address) from a 48-bit MAC address, ensuring uniqueness for Stateless Address Autoconfiguration (SLAAC).

• Splits the 48-bit MAC address in half.
• Inserts the 16-bit value 'FFFE' in the middle.
• Inverts the 7th bit (universal/local bit) of the original MAC address's first octet.

Memory trick: MAC to EUI: Split, FFFE, Flip the 7th.

A type of copper networking cable that contains an outer metallic foil or braid shielding layer in addition to the twisted pairs, designed to reduce electromagnetic interference (EMI) and improve signal integrity.

• Offers better EMI/RFI protection than UTP.
• More expensive and thicker than UTP.
• Requires proper grounding for effective shielding.

Memory trick: Shielding makes cables strong against the storm.

A DiffServ Per-Hop Behavior (PHB) that provides a low-loss, low-latency, low-jitter service, suitable for real-time and mission-critical applications.

• Often implemented with strict priority queuing.
• Designed for 'virtual leased line' effect.
• Typically used for VoIP, video conferencing, real-time data.

Memory trick: EF is 'Extra Fast' for critical traffic.

Ethernet cables are categorized by their performance specifications, indicating the maximum data rate and frequency they can support. Higher categories offer better performance and reduced interference.

• Cat5: Up to 100 Mbps (100BASE-TX)
• Cat5e: Up to 1 Gbps (1000BASE-T)
• Cat6: Up to 1 Gbps (1000BASE-T) for longer distances, or 10 Gbps for shorter distances.

Memory trick: Speed Up Your Network, Choose Wisely.

Traffic Policing is a QoS mechanism that strictly enforces traffic rates by actively dropping or remarking packets that exceed a configured threshold. It's an immediate action taken at the ingress of a network device to protect network resources.

• Strictly enforces traffic rate limits.
• Actively drops or remarks non-conforming packets.
• Used at ingress to protect network resources.
• Can lead to packet loss for non-conforming traffic.

Memory trick: Police cars drop the rule-breakers.

A specific Differentiated Services Code Point (DSCP) value (46) used to mark network traffic that requires low-loss, low-latency, low-jitter, and assured-bandwidth characteristics, typically for real-time applications like VoIP.

• Commonly used for VoIP.
• Signals high priority and low latency requirements.
• Value is 46 (101110 in binary).
• Part of the Differentiated Services (DiffServ) architecture.

Memory trick: EF = Express Fast, for urgent packets.

A networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.

• Synchronizes time across devices.
• Uses UDP port 123.
• Crucial for log analysis and security.

Memory trick: NTP: Never Tardy Protocol, keeps time perfect.

SNMP is an application-layer protocol used for organizing and exchanging information between network devices. It enables network administrators to monitor network performance, find and solve network problems, and configure network devices.

• Used for network device management and monitoring.
• Uses agents on devices and a manager for collection.
• Operates on UDP ports 161 (requests) and 162 (traps).

Memory trick: SNMP makes monitoring Simple, Not Managing Painful.

The initial steps in QoS where network traffic is identified and categorized, then tagged with a specific value (e.g., DSCP) to indicate its priority or required treatment.

• First step in QoS implementation.
• Identifies different types of traffic (e.g., VoIP, video, data).
• Uses fields like Differentiated Services Code Point (DSCP) for marking.

Memory trick: Classify Carefully, Mark Meaningfully, or Calls Crash.

A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network.

• Translates domain names to IP addresses.
• Essential for web browsing and email.
• Uses a hierarchical structure of servers.

Memory trick: DNS: Domains Naming System, finds numbers for names.

The highest Syslog severity level (level 0), indicating that the system is unusable, often due to a crash, and requires immediate attention.

• Severity level 0.
• Most critical log message type.
• Often associated with system failures or crashes.

Memory trick: An 'Emergency' is the ultimate system-stopping crisis.

A network protocol that dynamically assigns IP addresses and other network configuration parameters to devices connected to a network.

• Automates IP address assignment.
• Reduces manual configuration errors.
• Manages IP address leases.

Memory trick: DHCP: Delivering Home Connections Promptly.

A set of technologies that guarantee a certain level of performance for data flow over a network.

• Prioritizes traffic types.
• Ensures bandwidth for critical applications.
• Reduces latency and jitter for real-time services.

Memory trick: QoS: Quickly On Schedule, traffic gets priority.

IPv6 is the latest version of the Internet Protocol, designed to replace IPv4, primarily to provide a much larger address space and improve network efficiency and security.

• Uses 128-bit addresses, compared to IPv4's 32-bit addresses.
• Supports 3.4 x 10^38 unique addresses.
• Eliminates the need for Network Address Translation (NAT) in most cases.

Memory trick: Six is Super Sized, Solving Shortages.

A field in a Syslog message that indicates the source program or process that generated the log, helping to categorize messages by origin.

• Ranges from 0 to 23.
• Examples: kernel, user-level, mail system, system daemons, security/authorization.
• Used for filtering and routing logs.

Memory trick: The 'Facility' is like the department or building the message came from.

The duration for which a DHCP client can use an assigned IP address before it needs to renew or request a new one.

• Set by the DHCP server.
• Can be configured to vary based on network needs.
• Impacts IP address availability and network traffic.

Memory trick: Lease time is like renting an apartment; you have it for a set duration.

The standard UDP port number that Syslog uses for transmitting log messages over a network.

• UDP Port 514 is the default.
• Must be open on Syslog server firewall.
• TCP can also be used, often on port 6514, but UDP 514 is most common.

Memory trick: 514 is the Syslog door, UDP's log-store.

An IEEE standard for wireless local area networks, also known as Wi-Fi 5, designed for high-throughput data transfer in the 5 GHz frequency band.

• Operates exclusively in the 5 GHz frequency band.
• Introduced MU-MIMO (Multi-User Multiple-Input, Multiple-Output) for downlink.
• Offers theoretical maximum data rates up to several Gbps.
• Utilizes wider channels (up to 160 MHz) and higher-density modulation.

Memory trick: AC for 'Accelerated' and 'Advanced' wireless.

UTP cable is a type of copper cable used in local area networks, consisting of pairs of wires twisted together to reduce electromagnetic interference.

• Most common type of cable for Ethernet LANs.
• Available in different categories (e.g., Cat5e, Cat6, Cat6a) supporting various speeds.
• Terminated with RJ-45 connectors.

Memory trick: Twisted Pairs are the Top Pick for Typical PC Ports.

PaaS is a cloud computing service model that provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app. It sits between IaaS and SaaS.

• Provider manages hardware, OS, middleware, runtime.
• Customer manages applications and data.
• Ideal for developers who want to focus on coding, not infrastructure.
• Examples: Google App Engine, AWS Elastic Beanstalk, Heroku.

Memory trick: I-P-S: 'I' control hardware, 'P' control apps, 'S' control nothing.

The process of dividing a large IP network into smaller, more manageable subnetworks, improving efficiency, security, and reducing broadcast traffic.

• Uses a subnet mask to differentiate network and host portions of an IP address.
• Number of usable hosts = 2^h - 2, where 'h' is the number of host bits.
• Subnetting helps conserve IP addresses and manage network traffic.

Memory trick: Count the hosts, find the mask.

Cloud private connectivity solutions (e.g., AWS Direct Connect, Azure ExpressRoute) establish a dedicated, private network connection between an on-premises environment and a public cloud provider. These connections bypass the public internet, offering improved security, consistent bandwidth, and lower latency.

• Dedicated, private physical connection.
• Bypasses the public internet.
• Offers consistent bandwidth and lower latency.
• Enhanced security for sensitive data transfer.

Memory trick: Private Link: 'P' for 'Private' and 'Performance' bypasses the public.

An IPv6 Global Unicast Address (GUA) is an address that is globally unique and routable on the IPv6 internet. It is equivalent to a public IPv4 address and is primarily used for communication between different IPv6 networks across the globe.

• Globally unique and routable.
• Starts with binary 001 (currently 2000::/3 prefix).
• Used for internet communication.
• Composed of a global routing prefix, subnet ID, and interface ID.

Memory trick: L-U-G: 'Local' link, 'Unique' site, 'Global' internet.

An unsolicited alert message sent by an SNMP agent to an SNMP manager to notify of a significant event.

• Proactive notification mechanism.
• Used for critical events (e.g., link down, authentication failure).
• Reduces polling overhead for managers.

Memory trick: A 'Trap' catches attention with a sudden alert.

Subnet mask calculation determines the number of hosts and subnets available within a given IP address range by dividing the network.

• The number of usable hosts is 2^n - 2, where 'n' is the number of host bits.
• A smaller subnet mask (fewer bits for network portion) means more hosts per subnet.
• Efficiency involves choosing a mask that meets host requirements with minimal wasted addresses.

Memory trick: Host Need = Bits Borrowed for Mask.

Fiber optic cables transmit data using light pulses and are categorized by their mode of light propagation: single-mode and multi-mode.

• Immune to electromagnetic interference (EMI).
• Single-mode for long distances, multi-mode for shorter distances.
• Offers higher bandwidth and security than copper cables.

Memory trick: Distance, Interference, Speed: Define the Cable.

A 32-bit number that divides an IP address into network and host portions, allowing for efficient allocation and management of IP addresses within a network.

• Determines the size of a subnet.
• Consists of consecutive '1's for the network portion and '0's for the host portion.
• Expressed in dotted-decimal format or CIDR notation (e.g., /24).

Memory trick: Hosts Need Bits, Bits Make Masks

Wireless networks operate on either the 2.4 GHz or 5 GHz frequency bands, each with distinct characteristics regarding range, speed, and interference.

• 2.4 GHz: Longer range, better penetration, lower speed, more interference.
• 5 GHz: Shorter range, less penetration, higher speed, less interference.
• Interference on 2.4 GHz from microwaves, Bluetooth, cordless phones.

Memory trick: Fast 5s, Slow 2.4s, Crowded Airwaves, Clearer Views

The industry-standard protocol for VLAN tagging on Ethernet frames, which allows multiple Virtual Local Area Networks (VLANs) to share a single physical network link (trunk port).

• Inserts a 4-byte tag into Ethernet frames
• Identifies the VLAN ID (VID)
• Enables trunking for multiple VLANs
• Replaced Cisco's proprietary ISL in most modern networks

Memory trick: 802.1Q puts the VLAN tag on the trunk.

A Cisco switch feature that allows a single access port to carry traffic for both an IP phone (in a dedicated voice VLAN with QoS) and a connected PC (in a data VLAN).

• Automatically configures QoS for voice traffic.
• Simplifies deployment of IP phones.
• Requires the IP phone to support discovery protocols like CDP or LLDP-MED.

Memory trick: Voice VLAN: one port, two hats for phone and PC.

An IEEE 802.11 amendment designed to speed up the handoff process between access points in a wireless network, enabling seamless roaming.

• Minimizes re-authentication time for clients.
• Crucial for voice-over-Wi-Fi (VoWiFi) and real-time applications.
• Implemented on both APs and client devices.

Memory trick: Roaming 'R'equires 'R'apid 'R'econnection.