Networking fundamentals and CCNA-level reference content. The TCP/IP and OSI models, ethernet basics, encapsulation, IPv4 addressing, layer 2 fundamentals, and the Cisco IOS commands every network engineer reaches for. The foundations beneath the pillar guides.
Learn the difference between routers, switches, and firewalls in networking. This beginner-friendly guide explains how each device works using simple examples and Cisco concepts for CCNA study.
Cisco Modeling Labs 2.8 is now free, with a tier that lets you run routers, switches, and firewalls on your laptop. Here is what it unlocks for lab work and certs.
A working Cisco ASA cheat sheet: show version, write memory, failover, ACLs, NAT, and the troubleshooting commands you actually reach for under pressure.
IPv4 gives every networked device a 32-bit address split across classes and subnets. Here is how IPv4 addressing works, why it still runs the internet, and its limits.
Straight-through cables connect PC to switch or router; crossover cables connect like to like. Here is the pinout, color code, and when Auto-MDIX makes it moot.
IP routing is how routers pick a path and forward packets between networks. Here is the routing table, next hop, and longest-prefix match in simple terms.
Enabling SSH on a Cisco router or switch takes a hostname, domain name, RSA keys (3072-bit minimum on current IOS XE), a local user, and vty line login. Full config plus real verification output.
The Cisco IOS commands you actually run every day, grouped by job, with real output captured on IOS XE 17.18: status checks, interfaces, routing, switching, debugging, and filters.
Three reset methods that actually apply to Catalyst switches - write erase, factory-reset all, and Mode-button recovery - with real Catalyst 9000 output, and the config-register myth retired.
The Cisco ASA does not run CDP. Here is why, how to find the ASA from the connected switch with CDP, LLDP and the MAC table, and what to run on the ASA itself.
A Cisco switch gets its management IP on an SVI (usually VLAN 1 or a dedicated mgmt VLAN). Here is the config, the default gateway step, and SSH-readiness.
Get files onto a Cisco router with TFTP, SCP, or USB. Here is how to set up a TFTP server, use copy tftp: flash:, and avoid the common transfer gotchas.