Blog

EIGRP vs OSPF in 2026. The technical differences, the convergence story, vendor reality (EIGRP is still Cisco-only in practice), and the design implications for new vs existing networks.

EIGRP configuration on Cisco IOS XE: classic mode, named mode, network statements, passive-interface default, summarization, HMAC-SHA-256 authentication, and the production template.

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.

DUAL gives EIGRP sub-second failover via pre-computed feasible successors. The four key concepts (successor, FS, FD, RD), the feasibility condition that prevents loops, active states, and queries.

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 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.