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CCNA Library (74)

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Network (13)

OSI Model & TCP/IP IPv4 Addressing TCP vs UDP Subnetting IPv6 Basics ARP — Address Resolution Protocol ICMP — Internet Control Message Protocol TCP 3-Way Handshake Cabling & Media Standards MTU & Fragmentation WAN Connection Types Hierarchical Network Design Network Virtualization & Containers

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Cisco IOS Device Management Power over Ethernet (PoE)Cisco IOS File System Password Recovery & Configuration Register Network Troubleshooting Methodology

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MAC Address Table VLANs Trunks & 802.1Q Tagging Spanning Tree Protocol (STP)EtherChannel (Link Aggregation)Switching Operation CDP & LLDP — Neighbor Discovery BPDU Guard & Root Guard Catalyst Boot Process VTP — VLAN Trunking Protocol Rapid STP & MSTP Private VLANs (PVLAN)

Wireless (6)

Wireless LAN Basics WLAN Architectures — Autonomous, Centralized (WLC), Cloud, Embedded Wi-Fi Security — WEP, WPA, WPA2, WPA3 Wi-Fi 6, 6E, and 7 Features Wireless RF Fundamentals Access Point Operating Modes

IP Connectivity (10)

Inter-VLAN Routing Static Routing Default Routing Routing Decision Process FHRP — HSRP, VRRP & GLBP Layer-3 Switch & SVI Routing OSPF Single-Area Route Summarization IPv6 SLAAC & DHCPv6 IPv6 Transition Mechanisms

IP Services (11)

HSRP vs VRRP vs GLBP — FHRP Compared DHCP — Dynamic Host Configuration Protocol NAT & PAT DNS — Domain Name System NTP — Network Time Protocol Syslog QoS Basics SNMP — Simple Network Management Protocol IGMP & IGMP Snooping NTP Authentication & Security DHCP Relay & IP Helper

Security (10)

Access Control Lists (ACLs)Port Security DHCP Snooping AAA · RADIUS & TACACS+802.1X — Port-Based Network Access Control VPN Basics — IPsec & SSL Dynamic ARP Inspection (DAI)IP Source Guard (IPSG)Encryption Fundamentals Cybersecurity Threats & Mitigation

Automation (7)

REST APIs for Network Engineers Ansible for Network Engineers JSON, YAML & XML for Network Engineers NETCONF & YANG Python for Network Engineers SDN & Controller-Based Networking AI & ML in Network Operations

CCNP Library (15)

Browse all CCNP topics → SPAN, RSPAN & ERSPAN — Port Mirroring GRE Tunnels EIGRP OSPF Multi-Area IPv6 Routing — Static & OSPFv3 BGP Basics TCP Connection States Cisco AnyConnect / Remote Access VPN Cisco ISE Basics NetFlow & Flow-Based Monitoring gRPC & gNMI — Streaming Telemetry SD-WAN Concepts MPLS Basics Cisco DNA Center / Catalyst Center VRF Basics — Virtual Routing and Forwarding

Practice

Mock Exam Pricing

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IP Connectivity Simulator

OSPF Neighborship — Down to Full

Step two routers through OSPF adjacency formation. Inject real-world issues (Hello mismatch, ACL block, MTU mismatch) and see exactly where the state machine stalls. Practice quiz at the bottom.

DOWNCurrent State

—Active Packet

NONEDR / BDR Status

R1

R1 (Local)

ID: 1.1.1.1

HELLO

R2

R2 (Remote)

ID: 2.2.2.2

⚙️ Simulation parameters

Network media type

Inject interface issue

✉️ Packet on the wire

No packet sent yet. Click Advance handshake to see the next packet's contents.

Practice — neighbor states & their messages

Score: 0 / 0

Each round: a scenario or packet description. Take your time — Next button on both right and wrong.

Question

—

Drill this into reflex

When OSPF won't form an adjacency at 2 a.m.

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