Cisco IOS commands
How to Configure PortFast and BPDU Guard
This guide covers PortFast and BPDU Guard configuration for CCNA (200-301) and CCNP (ENARSI) exams, including hands-on labs, best practices, and how these features interact with RSTP. The switch port directly connected to an end station cannot create a bridging loop, so the port can safely skip straight to the forwarding state rather than progressing...
How to Troubleshoot DHCPv4 Problems
DHCP failures rarely announce their cause directly — a client just sits without an address, or ends up with the wrong one, and the actual reason could be anywhere from a bad cable to a missing relay command to a full address pool sitting quietly exhausted. What separates a fast fix from an hour of...
OSPF Encapsulation: How an OSPF Message Is Wrapped for Delivery
Open Shortest Path First (OSPF) operates at the network layer, but it doesn’t travel across a network on its own — every OSPF message gets wrapped in a stack of headers before it ever leaves a router’s interface. Understanding exactly how that wrapping works, layer by layer, is essential for reading a packet capture correctly...
Auto-MDIX on Cisco Devices: How It Works and How to Configure It
The port on a workstation, laptop, or server is called MDI (Media Dependent Interface). The port on a network switch, by contrast, is traditionally MDIX (Media Dependent Interface with Crossover). This distinction exists because someone has to “cross” the transmit and receive pairs somewhere in the connection, and historically, that job fell to whichever end...