EIGRP Metric and K Values Explained
The EIGRP composite metric formula, the five K values and why never to change them, the 64-bit wide metric for modern interfaces, and how to verify metrics in show output.
Archive
Latest posts — page 51
EIGRP DUAL Algorithm Deep Dive: Feasible Successors and the Real FD/RD Math
Everyone memorises RD < FD; nobody shows the arithmetic on a real router. Here it is on captured show ip eigrp topology output: one prefix with a feasible successor (409600 < 640000), one without (537600 > 512000), and a live failover where the route never left Passive.
QoS in Modern Networks: SD-WAN, Cloud, and Application-Aware Steering
QoS in 2026 is application-aware steering at the SD-WAN edge plus local queueing per tunnel. Why DSCP stops being honored at administrative boundaries, and how SD-WAN path conditioning compensates.
Voice and Video QoS on Cisco IOS XE
Voice and video are the use cases QoS exists for. Latency and jitter budgets, DSCP markings, IP phone trust, LLQ configuration, codec bandwidth math, and wireless voice via WMM.
QoS Queueing, Policing, and Shaping Compared
LLQ, CBWFQ, policing, and shaping each do something different. The three primitives, when to use which, hierarchical shaping for sub-rate WAN handoffs, and the production patterns.
QoS Classification, Marking, and Trust Boundaries
Classification and marking at the trust boundary are the foundation of every QoS deployment. The patterns (untrusted access ports, conditional trust for IP phones, explicit MQC marking) and the discipline that makes them work.
Cisco MQC (Modular QoS CLI): The Operator's Walkthrough
The Cisco MQC three-construct model (class-map, policy-map, service-policy) covers every QoS feature on IOS, IOS XE, and IOS XR. The grammar, common actions, hierarchical policies, and verification.
DSCP and IP Precedence Explained Byte by Byte
DSCP is the 6-bit Layer 3 marking that drives modern QoS. The byte format, the standardized PHBs (CS, AF, EF), Cisco's DSCP-to-CoS-to-MPLS-EXP mapping, and trust boundary discipline.
SD-WAN Security and the SASE Convergence
SD-WAN provides encryption and segmentation but creates an inspection gap. SASE fills that gap with cloud-delivered SWG, CASB, FWaaS, ZTNA, and DLP. The 2026 vendor landscape compared.
SD-WAN Deployment Models: Hybrid, Internet-Only, and Cloud On-Ramp
The four SD-WAN branch deployment models compared (hybrid, internet-only, cloud on-ramp, multi-cloud), HQ patterns, and the typical 18-30 month migration from MPLS-only.
Cisco vManage / SD-WAN Manager: The Operator's Walkthrough
Cisco vManage (now SD-WAN Manager) is the management plane of Cisco Catalyst SD-WAN. Templates, policies, dashboards, the REST API, HA model, and the operational realities at scale.
Cisco Catalyst SD-WAN Architecture: vManage, vSmart, vBond, WAN Edge
The four-component Cisco Catalyst SD-WAN (formerly Viptela) architecture: vManage, vSmart, vBond, and WAN Edge. OMP routing protocol, cEdge vs vEdge, fabric bring-up walkthrough.