Networking · Intermediate

CCNA online course

Routing, switching, and IPv4 fundamentals aimed at lab work and the current CCNA blueprint — written as explanations you can verify on a switch, not as a dump of exam dumps.

Who it is for

People moving into network operations or refreshing Cisco IOS basics.

You should already know

Comfort with binary math at a basic level and access to Packet Tracer, CML, or two physical switches.

You will be able to

  • Map the OSI layers to packets you can capture
  • Subnet an IPv4 block without a cheat app
  • Build VLANs and trunk them
  • Read a routing table and write a standard ACL

Lessons

  1. OSI model in practice Use the seven layers as a troubleshooting checklist, not a memorization chant.
  2. What Is Subnetting? Purpose, Broadcast Domains, and IPv4 Subnets Learn how IPv4 subnetting divides networks, reduces broadcast domains, supports routing and security, and helps design organized address plans.
  3. IEEE 802.1Q VLAN Tagging Overview Learn how IEEE 802.1Q tags VLAN traffic across Ethernet trunks, including tag fields, native VLANs, VLAN ID limits, Cisco configuration, verification, and ISL comparison.
  4. Routing basics Connected routes, static routes, and a first look at OSPF.
  5. Access control lists Standard and extended IPv4 ACLs, placement, and implicit deny.
  6. Computer Networks Explained: Fundamentals, Types, Components, and Communication Learn computer networking fundamentals, including devices, network types, topologies, protocols, OSI layers, addressing, performance, security, and troubleshooting.
  7. IEEE 802.1Q VLAN Tagging Overview Learn how IEEE 802.1Q VLAN tagging carries multiple VLANs across Ethernet trunks, including tag fields, VLAN IDs, native VLANs, ISL comparison, and troubleshooting.
  8. Configure and Verify NTP on Cisco IOS Devices Learn how to configure, authenticate, verify, and troubleshoot NTP time synchronization on Cisco IOS routers and switches.
  9. Configure OSPF for IPv4 Networks Learn to configure, verify, and troubleshoot single-area and basic multi-area OSPFv2 on Cisco IOS routers, including neighbors, areas, costs, DR elections, and default routes.
  10. Configure and Secure Password Access in Cisco IOS Learn to secure Cisco IOS privileged EXEC, console, VTY, and AUX access with enable secret, line passwords, local users, SSH, verification, and safe operational practices.
  11. Access and Trunk Ports Explained for CCNA Learn how Cisco access and trunk ports carry VLAN traffic, including 802.1Q tagging, native VLANs, voice VLANs, DTP, configuration, verification, and troubleshooting.
  12. Accessing Cisco IOS Devices Learn how to access, configure, secure, and verify Cisco IOS routers and switches using console, SSH, VTY, AUX, and privileged EXEC access.
  13. Address Resolution Protocol (ARP) Learn how ARP maps IPv4 addresses to MAC addresses, handles local and remote traffic, maintains ARP caches, and helps troubleshoot Ethernet connectivity.
  14. Administrative Distance (AD) Explained for CCNA Learn how Cisco routers use administrative distance, routing metrics, and longest-prefix matching to select IPv4 and IPv6 routes.
  15. Assign a Static MAC Address on a Cisco Switch Learn how to configure, verify, troubleshoot, change, and remove a static MAC address-table entry on a Cisco IOS switch.
  16. Configure a Switch Management IP Address Learn how to configure a Cisco Layer 2 switch management IP address, SVI, management VLAN, default gateway, verification commands, and secure remote access.
  17. Automatic Private IP Addressing (APIPA) Learn how APIPA assigns 169.254.x.x addresses when DHCP fails, what connectivity it permits, and how to troubleshoot APIPA issues for CCNA.
  18. Backing Up and Restoring Cisco IOS Device Configurations Learn how Cisco IOS stores configurations and how to save, verify, back up, transfer, restore, and troubleshoot router and switch configuration files.
  19. Cisco Device Boot Sequence: Routers and Switches Learn how Cisco routers and switches start: POST, bootstrap, IOS loading, configuration register behavior, startup-config, running-config, and boot troubleshooting.
  20. Broadcast Domains Explained for CCNA Learn how Ethernet broadcasts work, how switches, VLANs, routers, and Layer 3 switches define broadcast domains, and how to count and troubleshoot them for the CCNA.
  21. Cisco CCNA Online Course: Networking Fundamentals, Configuration, and Troubleshooting Study CCNA networking fundamentals with practical Cisco IOS labs covering switching, routing, VLANs, IPv4, IPv6, OSPF, wireless, security, services, automation, and troubleshooting.
  22. Cisco Internetwork Operating System (IOS) Fundamentals Learn Cisco IOS fundamentals, device memory, boot process, CLI modes, configuration management, verification commands, SSH access, and basic hardening for CCNA.
  23. Cisco Three-Layer Hierarchical Network Design Model Learn how Cisco access, distribution, and core layers organize campus networks for scalability, routing, policy control, performance, and resiliency.
  24. Collision Domains Explained Learn how Ethernet collisions occur, how CSMA/CD works, and how hubs, switches, bridges, routers, duplex settings, and VLANs affect collision and broadcast domains.
  25. Cisco IOS Command Modes Learn Cisco IOS command modes, prompts, hierarchy, navigation, context-sensitive help, configuration persistence, and safe CCNA CLI workflows.
  26. Cisco IOS Configuration Files: Running Configuration, Startup Configuration, and Backup Management Learn how Cisco IOS uses running-config and startup-config, how to save, compare, back up, restore, and erase configurations safely.
  27. Configure Allowed VLANs on Cisco Trunk Ports Learn how to restrict, add, remove, verify, and troubleshoot allowed VLANs on Cisco switch trunk ports, including EtherChannel considerations.
  28. Configure an IP Address on a Cisco Router Interface Learn how to configure and verify IPv4 and IPv6 addresses on Cisco IOS router interfaces, enable interfaces, verify routes, save changes, and troubleshoot connectivity.
  29. Configure Cisco IOS Login Banners Learn how to configure, verify, edit, and remove Cisco IOS MOTD, login, EXEC, incoming, and prompt banners.
  30. How to Configure Interface Descriptions in Cisco IOS Learn how to add, verify, edit, remove, and save Cisco IOS interface descriptions for clearer documentation and troubleshooting.
  31. Configure a Cisco Router as a DHCP Server Learn how to configure a Cisco IOS router as an IPv4 DHCP server, design address pools, verify leases, troubleshoot clients, and configure DHCP relay.
  32. Configure DNS on a Cisco IOS Device Learn how to configure Cisco IOS routers and switches as DNS clients, use local host mappings, enable basic IOS DNS service, verify resolution, and troubleshoot DNS failures.
  33. How to Configure IPv6 on a Cisco Router Learn how to enable IPv6 routing, configure router interfaces and link-local addresses, add static routes, verify connectivity, and troubleshoot IPv6 on Cisco IOS.
  34. Configure Multiarea OSPF on Cisco Routers Learn to design, configure, verify, summarize, and troubleshoot multiarea OSPF on Cisco IOS routers with practical examples and commands.
  35. Configure Router-on-a-Stick for Inter-VLAN Routing Learn to configure Cisco IOS router-on-a-stick inter-VLAN routing with 802.1Q trunking, router subinterfaces, host gateways, verification, and troubleshooting.
  36. How to Configure and Verify Hostnames on Cisco IOS Devices Learn how to set, verify, save, rename, and troubleshoot Cisco IOS router and switch hostnames using the CLI.
  37. Configure and Verify Cisco Switch Trunk Ports Learn how to configure, restrict, verify, and troubleshoot Cisco switch trunk ports using IEEE 802.1Q, native VLANs, allowed VLANs, and DTP.
  38. Configure VLANs on a Cisco Switch Learn how to create Cisco VLANs, assign access ports, configure 802.1Q trunks, manage VLANs, verify operation, and troubleshoot common CCNA VLAN problems.
  39. Configure VTP on Cisco Switches Learn how to configure, verify, and troubleshoot VTP on Cisco switches, including domains, modes, versions, pruning, authentication, and revision-number safety.
  40. CSMA/CD Explained: Carrier Sense Multiple Access with Collision Detection Learn how CSMA/CD manages shared half-duplex Ethernet, including collisions, jam signals, binary exponential backoff, slot time, errors, and duplex troubleshooting.
  41. Data Encapsulation in Networking Learn how data is encapsulated and decapsulated through the OSI and TCP/IP models, including TCP, IP, Ethernet, addressing, routing, MTU, and troubleshooting.
  42. Data Encapsulation in the OSI Model Learn how data moves through the OSI model as segments, packets, frames, and bits, including headers, trailers, addressing, routing, and decapsulation.
  43. Using the debug Command in Cisco IOS Learn how Cisco IOS debug commands work, how to filter and interpret output, and how to troubleshoot safely without overwhelming a network device.
  44. OSPF Designated Router (DR) and Backup Designated Router (BDR) Learn how OSPF elects DR and BDR routers on Ethernet and NBMA networks, including priorities, router IDs, neighbor states, Cisco IOS configuration, verification, and troubleshooting.
  45. Differences Between Network Switches and Bridges Learn how Ethernet bridges and switches forward frames, learn MAC addresses, separate collision domains, handle VLANs and broadcasts, and use STP to prevent Layer 2 loops.
  46. EIGRP Diffusing Update Algorithm (DUAL) Learn how EIGRP DUAL selects successors and feasible successors, prevents routing loops, handles failures, uses queries and replies, and avoids Stuck in Active conditions.
  47. Directly Connected Routes in Cisco Networks Learn how Cisco routers create, display, select, and use IPv4 and IPv6 directly connected and local routes.
  48. How to Display and Manage Cisco IOS Command History Learn how Cisco IOS command history works, including show history, command recall, session and line configuration, verification, troubleshooting, and security considerations.
  49. Domain Name System (DNS) Fundamentals for CCNA Learn DNS hierarchy, records, resolution, caching, transport, Cisco IOS configuration, and practical DNS troubleshooting for CCNA.
  50. Dynamic Host Configuration Protocol (DHCP) for CCNA Learn DHCP for CCNA: IPv4 configuration, DORA, leases, Cisco IOS DHCP servers, relay agents, verification, security, and troubleshooting.
  51. Dynamic NAT Configuration and Operation for CCNA Learn Dynamic NAT terminology, address pools, ACL selection, Cisco IOS configuration, verification, capacity planning, and troubleshooting.
  52. Dynamic Routing for CCNA Learn dynamic routing for CCNA: routing tables, route selection, RIP, OSPF, EIGRP, configuration, verification, convergence, and troubleshooting.
  53. EIGRP Network Statements and Wildcard Masks Learn how EIGRP network statements and wildcard masks select Cisco IOS interfaces, form neighbors, advertise routes, and support safe classless routing.
  54. EIGRP Auto-Summary: Behavior, Configuration, and Verification Learn how EIGRP auto-summary creates classful routes, affects VLSM and discontiguous networks, and how to configure, verify, and troubleshoot it on Cisco routers.
  55. EIGRP Configuration and Verification for Cisco Routers Learn how EIGRP works and how to configure, verify, troubleshoot, summarize, and control IPv4 routes on Cisco IOS routers.
  56. EIGRP Manual Route Summarization Learn how to calculate, configure, verify, and troubleshoot manual IPv4 route summarization in Cisco EIGRP, including classic and named mode.
  57. EIGRP Neighbors and Neighbor Adjacencies Learn how Cisco EIGRP discovers neighbors, forms and maintains adjacencies, verifies neighbor status, and troubleshoots failed IPv4 neighbor relationships.
  58. EIGRP Overview: Concepts, Operation, and Basic Configuration Learn EIGRP concepts, DUAL route selection, neighbors, metrics, tables, classic IPv4 configuration, verification, summarization, and troubleshooting on Cisco IOS.
  59. EIGRP Tables: Neighbor, Topology, and Routing Tables Learn how EIGRP neighbor, topology, and routing tables work together, including successors, feasible successors, route states, metrics, verification, and troubleshooting.
  60. Ethernet Frame Structure and Fields Learn Ethernet frame structure, including MAC addresses, EtherType, VLAN tags, payload padding, FCS, frame sizes, switching, routing, and troubleshooting.
  61. CCNA Extended Access Control Lists (ACLs) Learn how Cisco IOS IPv4 extended ACLs filter traffic by protocol, addresses, ports, ICMP types, direction, and interface, with configuration, verification, and troubleshooting examples.
  62. File Transfer Protocol (FTP) Learn how FTP transfers files, how control and data connections use TCP ports, how active and passive modes work, and why SFTP, FTPS, or HTTPS are safer choices.
  63. Frame Tagging Explained: VLAN Tags, Trunks, and 802.1Q Learn how 802.1Q frame tagging identifies VLANs across trunk links, how native VLANs handle untagged traffic, and how to troubleshoot Cisco VLAN trunks.
  64. Using Cisco IOS Context-Sensitive Help and Command Assistance Learn how to use Cisco IOS question-mark help, command completion, abbreviations, error messages, and verification commands in the CLI.
  65. Half-Duplex and Full-Duplex Ethernet Learn simplex, half-duplex, and full-duplex Ethernet, collision domains, CSMA/CD, auto-negotiation, duplex mismatches, and Cisco IOS troubleshooting.
  66. Routing Holddown Timers Explained Learn how routing holddown timers reduce distance-vector routing loops, how RIP timers work, and how to verify route failure behavior on Cisco IOS.
  67. How Ethernet Switches Learn MAC Addresses and Forward Frames Learn how Layer 2 switches build MAC address tables, learn source MACs, and forward, flood, filter, or discard Ethernet frames within VLANs.
  68. How Ethernet Switches Learn MAC Addresses Learn how Layer 2 switches build MAC address tables, forward known unicasts, flood unknown traffic, filter frames, age entries, and troubleshoot MAC moves.
  69. How to Create IPv4 Subnets Learn IPv4 subnetting step by step: calculate masks, CIDR prefixes, block sizes, network ranges, usable hosts, broadcasts, FLSM, VLSM, and verification.
  70. Hypertext Transfer Protocol (HTTP) Learn how HTTP clients and servers exchange web resources through requests and responses, including methods, headers, status codes, ports, versions, HTTPS, and troubleshooting.
  71. HTTPS: Secure Web Communication with TLS Learn how HTTPS uses TLS, certificates, public key infrastructure, and secure handshakes to protect HTTP traffic, plus deployment and troubleshooting guidance.
  72. IEEE Ethernet Standards for CCNA Learn how IEEE 802.3 Ethernet standards identify speed, copper and fiber media, connectors, distance limits, duplex operation, and common CCNA link designs.
  73. Cisco Inter-Switch Link (ISL) Overview Learn how Cisco ISL trunks carry multiple VLANs, how ISL compares with IEEE 802.1Q, legacy configuration commands, verification, and troubleshooting.
  74. Cisco IOS Device Interfaces: Identification, Status, and Basic Configuration Learn Cisco IOS interface naming, status interpretation, routed ports, switchports, SVIs, basic configuration, verification, troubleshooting, and safe administration.
  75. Internet Control Message Protocol (ICMP) for CCNA Learn how ICMP and ICMPv6 report IP errors, support ping and traceroute, handle TTL and path MTU discovery, and guide CCNA troubleshooting.
  76. Cisco IOS show Commands: Viewing and Verifying Device Status Learn Cisco IOS show commands for checking configurations, interfaces, VLANs, routing, neighbors, hardware, and troubleshooting device status.
  77. IPv4 Address Classes Learn legacy IPv4 Classes A through E, default masks, network and host portions, special ranges, and why modern networks use CIDR and VLSM.
  78. IP Address Types: IPv4 and IPv6 Addressing Explained Learn IPv4 and IPv6 address types, CIDR, private and public ranges, unicast, multicast, DHCP, SLAAC, special-use addresses, and troubleshooting.
  79. IP Routing Explained: How Routers Forward Packets Learn how IPv4 routing works, including default gateways, routing tables, longest-prefix match, next hops, Cisco IOS verification, and common routing failures.
  80. IPv4 Header Fields and Packet Processing Learn every IPv4 header field, including IHL, DSCP, fragmentation, TTL, protocol, checksum, addressing, encapsulation, and packet-capture analysis.
  81. IPv6 Address Format and Notation Learn how IPv6 addresses are structured, written, shortened, expanded, validated, and interpreted, including prefixes, scopes, and common address types.
  82. IPv6 Address Types for CCNA Learn IPv6 address types, prefixes, scopes, multicast, anycast, address assignment, and Cisco IOS verification commands for CCNA.
  83. IPv6 EUI-64 Interface Identifier Calculation Learn how to calculate an IPv6 EUI-64 interface identifier from a 48-bit MAC address and configure it on Cisco IOS.
  84. IPv6 Global Unicast Addresses Learn how IPv6 global unicast addresses are structured, subnetted, assigned, configured, verified, and routed in a CCNA-level network.
  85. IPv6 Link-Local Addresses Learn how IPv6 link-local addresses work, how Cisco IOS creates and configures them, and how to verify, route, and troubleshoot FE80::/10 addresses.
  86. IPv6 Overview for CCNA Learn IPv6 addressing, notation, address types, SLAAC, DHCPv6, Neighbor Discovery, routing, Cisco IOS configuration, coexistence, and troubleshooting for CCNA.
  87. IPv6 Unique Local Addresses (ULA) for CCNA Learn IPv6 Unique Local Addresses: FC00::/7, FD00::/8, random global IDs, /64 subnetting, SLAAC, routing, Cisco IOS configuration, verification, and troubleshooting.
  88. Layer 2 Switching: Ethernet Frames, MAC Tables, and Cisco Verification Learn how Layer 2 switches forward Ethernet frames, learn MAC addresses, separate collision domains, prevent loops, and troubleshoot switching issues for CCNA.
  89. Link-State Advertisements (LSAs) in OSPF Learn how OSPF LSAs describe topology, flood through areas, build the LSDB, and produce intra-area, inter-area, and external routes.
  90. Local Area Networks (LANs): Concepts, Components, and Cisco Networking Fundamentals Learn LAN fundamentals for CCNA: Ethernet switching, devices, media, VLANs, IP addressing, wireless integration, security, STP, and Cisco IOS troubleshooting.
  91. MAC Addresses: Ethernet Layer 2 Addressing for CCNA Learn how Ethernet MAC addresses identify local interfaces, how switches learn and forward frames, how MACs change across routed hops, and how to troubleshoot them.
  92. Mapping Hostnames to IP Addresses: DNS and Hostname Resolution Learn how DNS, hosts files, and Cisco IOS map hostnames to IPv4 and IPv6 addresses, including lookups, caching, configuration, and troubleshooting.
  93. Cisco Device Memory Types: RAM, ROM, Flash, and NVRAM Learn how RAM, ROM, flash, and NVRAM work in Cisco routers and switches, including bootup, IOS storage, configurations, commands, and troubleshooting.
  94. Network Address Translation (NAT): Definition, Types, and Cisco Configuration Learn how IPv4 NAT works, compare static NAT, dynamic NAT, and PAT, and configure and troubleshoot NAT on Cisco IOS routers.
  95. Network Time Protocol (NTP) for CCNA Learn NTP fundamentals, stratum, Cisco IOS configuration, verification, security, design, and troubleshooting for CCNA.
  96. OSI Reference Model: The Seven Networking Layers Learn the seven OSI model layers, their functions, protocols, addressing, data units, encapsulation process, and CCNA troubleshooting techniques.
  97. OSPF Areas Explained: Backbone, Standard, Stub, and NSSA Areas Learn how OSPF areas improve scalability, compare normal, stub, totally stubby, NSSA, and totally NSSA areas, and configure and troubleshoot them in Cisco IOS.
  98. Configuring OSPF Plaintext Authentication Learn to configure, verify, and troubleshoot Cisco IOS OSPF simple password authentication, including interface and area-wide settings.
  99. Configure OSPF MD5 Authentication Learn how to configure, verify, and troubleshoot OSPFv2 MD5 message-digest authentication between Cisco IOS routers.
  100. OSPF Neighbor Discovery and Adjacency Formation Learn how OSPF routers discover neighbors with Hello packets, progress through neighbor states, elect DR and BDR routers, synchronize LSDBs, and troubleshoot incomplete adjacencies.
  101. OSPF Neighbor States Explained Learn every OSPF neighbor state from Down to Full, understand DR and BDR behavior, and troubleshoot adjacency problems using Cisco IOS verification commands.
  102. OSPF Overview for CCNA Learn OSPF for CCNA: link-state operation, neighbors, areas, router IDs, metrics, DR and BDR elections, Cisco IOS configuration, verification, and troubleshooting.
  103. OSPF Route Summarization for CCNA Learn how to configure and verify OSPF route summarization on Cisco IOS using ABR area range and ASBR summary-address commands.
  104. Cisco PAT Configuration and NAT Overload Learn Cisco IOS PAT configuration using an outside interface or NAT pool, including ACLs, verification commands, troubleshooting, and design limits.
  105. Cisco IOS Pipe Function: Filtering Command Output Learn how to use the Cisco IOS pipe character with include, exclude, begin, and section filters to search and review CLI command output.
  106. Switch Port Security Configuration and Verification Learn how Cisco switch port security limits MAC addresses on access ports, including configuration, secure MAC learning, violation modes, aging, verification, and troubleshooting.
  107. How Cisco IOS Devices Power On and Boot Learn how Cisco routers and switches boot: POST, bootstrap, IOS image loading, configuration loading, boot variables, ROMMON, and recovery.
  108. Private IP Addresses in IPv4 Networking Learn RFC 1918 private IPv4 ranges, subnetting, NAT/PAT, routing behavior, address planning, VLAN design, and troubleshooting.
  109. Cisco Reliable Transport Protocol (RTP) Learn how Cisco Reliable Transport Protocol supports reliable EIGRP routing updates using acknowledgments, sequencing, multicast, unicast retransmissions, and IP protocol 88.
  110. EIGRP Reported Distance and Feasible Distance Explained Learn how EIGRP calculates reported distance and feasible distance, selects successors, keeps loop-free backup paths, and handles route failures.
  111. RIP Configuration on Cisco Routers Learn how to configure, verify, and troubleshoot RIPv2 on Cisco IOS routers, including network statements, auto-summary, passive interfaces, default routes, timers, and common failures.
  112. RIP Routing Information Protocol Overview Learn RIP distance-vector routing, hop-count metrics, RIPv1, RIPv2, RIPng, Cisco IOS configuration, verification, timers, and troubleshooting for CCNA.
  113. Route Poisoning in Distance-Vector Routing Learn how route poisoning prevents distance-vector routing loops, how RIP uses metric 16, and how poisoning relates to poison reverse, split horizon, timers, and triggered updates.
  114. Routing Between VLANs Learn why inter-VLAN routing is required and configure router-on-a-stick and multilayer-switch routing with Cisco IOS verification and troubleshooting.
  115. Routing Metrics Explained for CCNA Learn how routing metrics rank paths, how metrics differ from administrative distance, and how RIP, OSPF, and EIGRP select routes.
  116. Routing Tables Explained for CCNA Learn how Cisco routers use IPv4 and IPv6 routing tables, longest prefix match, administrative distance, metrics, static and dynamic routes, default routes, and troubleshooting commands.
  117. Run Privileged EXEC Commands from Global Configuration Mode Learn how to use Cisco IOS do to run show, verification, and save commands from global configuration mode without changing CLI context.
  118. Cisco IOS service password-encryption Command Learn how Cisco IOS service password-encryption creates reversible Type 7 password obfuscation, how to verify it, and why enable secret and AAA are more secure.
  119. Monitoring Cisco IOS Running Processes with show processes Learn how to use Cisco IOS show processes to read CPU utilization, interpret process fields and states, and investigate sustained high CPU safely.
  120. Simple Network Management Protocol (SNMP) for CCNA Learn SNMP architecture, MIBs, OIDs, operations, versions, security, ports, Cisco IOS configuration, monitoring data, and troubleshooting for CCNA.
  121. Split Horizon in Distance Vector Routing Protocols Learn how split horizon prevents routing loops in distance-vector protocols such as RIP and EIGRP, with a three-router example, Cisco IOS lab, and troubleshooting guidance.
  122. Cisco Standard ACLs: Configuration, Placement, and Packet Filtering Learn how Cisco standard IPv4 ACLs use source addresses, wildcard masks, first-match processing, implicit deny, interface direction, and destination-side placement.
  123. Configure and Verify Static NAT on Cisco Routers Learn how static NAT creates fixed one-to-one IPv4 mappings, then configure, verify, and troubleshoot static NAT on a Cisco IOS router.
  124. Cisco CCNA Static Routes: Configuration and Verification Learn how IPv4 static routes work, configure Cisco IOS next-hop and exit-interface routes, and verify remote connectivity with show ip route and ping.
  125. Subnet Masks Explained: Network and Host Portions of an IPv4 Address Learn how IPv4 subnet masks separate network and host bits, use CIDR prefix lengths, and calculate a network address with binary AND.
  126. EIGRP Successor and Feasible Successor Explained Learn how EIGRP selects a successor, evaluates feasible successors with FD and RD, prevents loops, and reacts when a primary route fails.
  127. TCP and UDP Port Numbers and Well-Known Services Learn how TCP and UDP ports identify applications, how client-server sessions use source and destination ports, and memorize common CCNA service ports.
  128. TCP/IP Suite of Protocols Learn the TCP/IP suite, its four-layer model, encapsulation, and the roles of DNS, HTTP, TCP, UDP, IP, ICMP, ARP, and Ethernet for CCNA study.
  129. TCP/IP Reference Model: Layers, Protocols, Encapsulation, and OSI Comparison Learn the four TCP/IP reference model layers, their responsibilities, common protocols, encapsulation, troubleshooting uses, and comparison with the seven-layer OSI model.
  130. Telnet Protocol for Remote Device Access Learn how Telnet provides remote CLI access, why it uses TCP port 23, how client-server connections work, and why SSH is preferred for secure administration.
  131. Cisco IOS traceroute Command: Path Discovery and Troubleshooting Learn how Cisco IOS traceroute discovers Layer 3 hops, how to read response symbols, and how to troubleshoot failed or filtered paths.
  132. Transmission Control Protocol (TCP) Explained Learn how TCP provides reliable, ordered, connection-oriented transport using ports, handshakes, acknowledgments, retransmissions, flow control, and connection termination.
  133. Trivial File Transfer Protocol (TFTP) for CCNA Learn how TFTP uses UDP port 69, transfer identifiers, RRQ and WRQ packets, Cisco IOS configuration and image transfers, security limitations, and troubleshooting.
  134. OSPF LSA Types: Type 1 Through Type 5 Learn how OSPF Type 1 through Type 5 LSAs work, who originates them, what they contain, where they flood, and how to verify them on Cisco IOS.
  135. Types of Routing Protocols: Static, Dynamic, Distance Vector, Link-State, and Path Vector Learn how static routing, RIP, EIGRP, OSPF, IS-IS, and BGP exchange routes, select paths, converge, and fit into CCNA networks.
  136. Ethernet Unicast, Multicast, and Broadcast MAC Addresses Learn how Ethernet destination MAC addresses identify one device, a device group, or every device in a VLAN, and how switches forward each frame type.
  137. Use Cisco Discovery Protocol (CDP) to Identify Directly Connected Devices Learn how CDP discovers directly connected Cisco devices and how to interpret show cdp neighbors and detailed neighbor output.
  138. Cisco IOS Extended Ping: Test Reachability, Source Paths, and MTU Learn how to use Cisco IOS extended ping to select a source address, verify return paths, test MTU, interpret results, and troubleshoot routing and ICMP problems.
  139. Using Telnet on Cisco IOS Devices Learn how to start, suspend, resume, and close Telnet sessions in Cisco IOS, configure VTY lines for incoming access, troubleshoot connections, and understand Telnet security limits.
  140. User Datagram Protocol (UDP) Explained Learn how UDP works at OSI Layer 4, including connectionless delivery, datagram structure, header fields, UDP versus TCP, and common use cases.
  141. VLAN Trunking Protocol (VTP) Overview Learn how Cisco VTP synchronizes VLAN database information, how VTP domains and advertisements work, and why VTP is different from VLAN trunking.
  142. VLANs Explained: Broadcast Domains, Benefits, and Basic Switch Configuration Learn how VLANs segment Layer 2 networks, contain broadcasts, use access and trunk ports, extend across switches, and support inter-VLAN routing.
  143. VTP Modes Explained: Server, Client, and Transparent Learn how Cisco VTP server, client, and transparent modes manage VLANs, synchronize VLAN databases, advertise changes, and forward VTP messages.
  144. What Is a Network Bridge? Learn how a Layer 2 network bridge connects LAN segments, separates collision domains, forwards Ethernet frames by MAC address, and compares with hubs and switches.
  145. What Is a Network Hub? Learn how Ethernet network hubs operate as Layer 1 multiport repeaters, why hubs create shared collision domains, and how switches improve LAN performance.
  146. What Is a Network Switch? Functions, MAC Tables, and Frame Forwarding Learn how Ethernet network switches connect LAN devices, learn MAC addresses, build forwarding tables, and selectively forward, filter, or flood frames.
  147. What Is a Router? Learn what a router does, how it forwards packets between IP networks, how default gateways and routing tables work, and how routers differ from switches and bridges.
  148. What Is an Access Control List (ACL)? Cisco CCNA Guide Learn how Cisco ACLs filter packets, how standard and extended ACLs differ, wildcard masks, rule order, interface direction, configuration, and verification.
  149. What Is an IP Address? IPv4 Addressing Basics Learn how IPv4 addresses identify network interfaces, how subnet masks divide network and host portions, how DHCP and NAT work, and how to view IP settings in Windows and Linux.
  150. What Is Ethernet? IEEE 802.3 LAN Technology Explained Learn what Ethernet is, how IEEE 802.3 defines LAN media, frames, speeds, and access methods, and how modern switched Ethernet differs from legacy shared networks.
  151. Secure Shell (SSH) Protocol Learn how SSH securely provides remote command-line access to routers and hosts, how SSH clients and servers work, and why SSH is safer than Telnet.
  152. What Is IPv4 Subnetting? Learn IPv4 subnetting, broadcast domains, subnet masks, /24 to /25 splitting, routing, VLANs, security segmentation, and common troubleshooting issues.
  153. Wildcard Masks Explained for Cisco ACLs and OSPF Learn how Cisco wildcard masks work, calculate inverse masks from subnet masks, and use them in standard ACLs, extended ACLs, and OSPF.
  154. Computer Networks Explained: Devices, Data Exchange, and LANs Learn how computer networks connect devices, exchange packets, use switches and routers, and link a home LAN to the Internet.
  155. VLAN Frame Tagging Explained: IEEE 802.1Q, Native VLANs, and Trunk Links Learn how IEEE 802.1Q VLAN tagging works, including access ports, trunk links, native VLANs, allowed VLANs, frame fields, verification, and troubleshooting.