Fundamentals

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.

76 posts

QoS

QoS on a Router: A Practical Cisco IOS XE Walkthrough

How to build a working QoS policy on a Cisco router: MQC class maps, policy maps, the LLQ + CBWFQ model, and the shaper rule that makes it actually engage.

May 27, 2026 5 min read

BGP weight Cisco path attribute feature image, PingLabz

BGP

BGP Weight: The Cisco-Only Path Attribute (and When to Use It)

BGP weight is the first tiebreaker in the path-selection algorithm, set locally and never propagated. The three ways to set it, how it compares to LOCAL_PREF, and worked examples.

May 24, 2026 5 min read

QoS for VoIP across MPLS WAN feature image, PingLabz

QoS

QoS for VoIP Across an MPLS WAN

End-to-end QoS for VoIP across an MPLS L3VPN: DSCP marking, the LLQ + CBWFQ policy at the CE edge, and the DSCP-to-MPLS-EXP mapping the carrier needs.

May 24, 2026 5 min read

OSPF

OSPF Cost: Reference Bandwidth, Manual Overrides, and Gotchas

OSPF cost explained: the formula, the default reference bandwidth that breaks at 1 Gbps and above, manual overrides per interface, ECMP, and the misconfigurations to avoid.

May 23, 2026 5 min read

EtherChannel and Spanning Tree feature image, PingLabz

STP

STP and EtherChannel: When They Collide and Who Wins

How EtherChannel hides bundled links from STP, the bundling protocols (LACP, PAgP, on), the dangerous failure modes, and why LACP active on both sides is the only safe configuration.

May 23, 2026 5 min read

RSTP Rapid Spanning Tree Protocol feature image, PingLabz

STP

RSTP: Rapid Spanning Tree Protocol Explained (802.1w)

RSTP (802.1w) explained: the new port roles, three-state model, proposal/agreement handshake, Rapid-PVST+ vs MST, and the real show spanning-tree output.

May 22, 2026 6 min read