Understanding IPv4: The Internet’s Original Addressing System
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.
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.
The OSI model's seven layers explain how data moves from application to wire. Here is each layer, the key protocols, and how to use the model for troubleshooting.
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, a local user, and vty line login. Here is the full config plus verification.
Fifty Cisco IOS commands every network admin and CCNA candidate should have in muscle memory, grouped by config, interface, routing, security, and troubleshooting.
SVIs (Switch Virtual Interfaces) are logical VLAN interfaces that enable a Layer 3 switch to route between VLANs and provide management access. Master SVI creation, IP routing enablement, and troubleshooting SVI states.
show interface status tells you more than up/down. Here are five tips for reading it quickly: port status, VLAN, speed/duplex, errdisable, and description use.
Factory resetting a Cisco switch means clearing the config, VLAN database, and sometimes the boot variable. Here are the safe methods and pre-reset prep.
Checking CDP neighbors on a Cisco ASA is a two-command job once CDP is enabled. Here is how to turn it on, read show cdp neighbors, and map your topology.
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.