13 posts
A practical guide to reading BGP looking glass output — how to interpret the AS path, origin AS, next hop, RPKI status, and route collectors, and how to use a looking glass to diagnose reachability problems, suboptimal routing, and hijacks.
Cloudflare runs both a recursive resolver (1.1.1.1) and an authoritative DNS service, and they do completely different jobs. This is the clearest way to explain the difference between the two halves of every DNS lookup.
Network engineering teams have always had a diagram problem. Lucidchart solves a lot of it — here's what it does well, where it fits in real workflows, and the honest limitations you should know going in.
Most online MTU calculators stop at 'GRE adds 24 bytes.' Real networks stack encapsulations — VXLAN over IPsec, GRE over IPsec, MPLS-then-VXLAN — and need the actual adjust-mss command for the device you're configuring. So I built one that does both.
A comprehensive guide to prefix-lists and route-maps in Cisco BGP — what they do, how they differ from ACLs, when to use each, and practical configurations for inbound/outbound BGP policy.
Everything you need to know about Autonomous System Numbers — what an AS is, the difference between public and private ASNs, how they work in BGP, 2-byte vs 4-byte ASNs, how to look one up, and the process for getting your own.
A deep dive into Bidirectional Forwarding Detection — why BGP's default failure detection is dangerously slow, how BFD provides sub-second link failure detection, and how to configure it on Cisco IOS-XE, IOS-XR, and NX-OS.
How a government censorship order, a leaked more-specific route, and one upstream provider that didn't filter turned into a global internet outage that took YouTube offline for nearly two hours in 2008 — and what it proved about BGP's fundamental trust problem.
A clear, high-level breakdown of DNSSEC — the problem it solves, how cryptographic signing creates a chain of trust from the root zone down to your domain, and why every DNS owner should understand it.
A complete breakdown of all five BGP EVPN route types defined in RFC 7432 and RFC 8365 — what information each carries, when each is generated, and how they work together to build a VXLAN fabric.
A deep technical breakdown of VXLAN EVPN — what the underlay and overlay are, how VTEPs encapsulate traffic, why BGP replaced flood-and-learn, and how symmetric IRB enables Layer 3 routing across the fabric.
Understanding Nexus Dashboard's two-network design, persistent IP addresses, BGP configuration for L3 deployments, and required firewall ports for ND 4.2.
A practical guide to Nexus Dashboard — what it is, how it replaces DCNM, and how to get the most out of its multi-site visibility features.
