LevelUp your I.T skills for the ever evolving job market

Gain practical real-world and in-demand experience with LevelUp I.T.'s articles, examples, labs, public and private repos!

Featured posts

MLAG shares state over a dedicated peer link; EVPN multihoming shares it through BGP

EVPN multihoming vs MLAG on Cumulus Linux: what actually breaks

EVPN multihoming vs MLAG: what actually breaks Both make two leaf switches look like one LACP partner to a dual-homed server. Both forward on both links. So which one holds up when something fails? Two labs on Cumulus Linux, identical wiring, four failure scenarios, every probe accounted for.

11 min read

Active/Active Firewalls the Routing Way: Palo Alto, BGP, and a 3-Second Hold Timer

infiniband verbs banner, hand-drawn excalidraw style: green RNIC chip icon

Skip the Kernel: InfiniBand Verbs in Five Minutes

One Adapter, Many Tenants: InfiniBand Partitions and SR-IOV, From the Firmware to the Wire

Routing Kubernetes into a CLOS fabric with Cilium BGP

Join now

Courses

Fabric lab: build a small cloud, end to end

Build a Cloud-Style Fabric Lab

An 11-part, copy-paste-reproducible build of a small cloud: leaf-spine VXLAN/EVPN fabric, Kubernetes with Cilium BGP, and Active/Active firewalls, all virtual, all on one box.

Members only

Mastering BGP

Mastering BGP delves into its architectural strengths: reliability (TCP foundation, keepalives), stability (MAI, dampening, route refresh), scalability (reflection, confederations, selective propagation), and flexibility (policy-driven, path attributes, communities).

Mastering IS-IS

IS-IS, a robust link-state routing protocol, is key for scalable networks. This series demystifies IS-IS from its Layer 2 operations, NSAP addressing, and hierarchical design to advanced traffic engineering with practical Juniper configurations. Master IS-IS for high-performance network designs.

Network Automation with GO

Hello and welcome to "Network Automation with Go," a blog series designed for network engineers and developers. We'll explore how Go's speed, concurrency, and simplicity can help you build powerful, efficient, and scalable network automation solutions. Get ready to level up your skills!

View all

Join now

EVPN multihoming vs MLAG on Cumulus Linux: what actually breaks

11 min read

Cisco Nexus EVPN to Cilium: one request, checkpoint by checkpoint

Where the Packet Died: One Request, Checkpoint by Checkpoint, Across a Nexus EVPN Fabric and Cilium

Your pod is Running, your Service exists, the curl still hangs. Most Kubernetes traffic diagrams stop at a Load Balancer cloud. On bare metal that cloud is a Cisco Nexus EVPN fabric. Here is one HTTPS request traced all the way to the pod, with the command that proves every hop.

6 min read

EVPN MAC Mobility, Watched Live: RFC 7432 Sequence Numbers Across a Cisco and Juniper Multi-DC Fabric

A MAC address leaves a Cisco datacenter and reappears behind a Juniper leaf in another one. Watch RFC 7432 do its job across the multisite DCI: the counter climbing 0, 1, 2, the losing leaf yielding, and the exact BGP packets that carried each move, captured on the interconnect.

8 min read

evpn route types explained from a live fabric

EVPN Route Types: A Deep Dive From a Live Fabric

Type-2 gets all the attention, but a datacenter fabric runs on five core EVPN route types and quietly depends on every one. Here is what each actually carries, decoded from a live multihomed fabric, including the two types MLAG labs never get to show you.

7 min read

Replicating a Two-DC EVPN Datacenter in Containerlab

One git clone, four commands, and 20 minutes later a client curls an anycast VIP by DNS name through two firewalls into whichever datacenter the control plane picked. 39 nodes, zero manual configuration. Here is how the whole lab became a git repo.

6 min read

Testing an Agentic NOC: How to Earn Trust

Part 7 of the Agentic NOC series. How you earn the right to trust a system that watches and sometimes changes your network: 131 offline tests against real captured output, mutated-data fault detection, a live 30-fault campaign, and the worst bug of all, a monitor that mistakes silence for success.

6 min read

A green verified checkmark with the detect-remediate-verify cycle

Results: What the Agentic NOC Actually Does

Part 6 of the Agentic NOC series. Real captured runs: a request crossing both protocol layers to a live switch, the planner fanning out, a 30-fault detect-remediate-verify loop, the monitor self-healing then escalating on a flap and refusing to fake health.

7 min read

Decoding a Two-Datacenter Traceroute, Hop by Hop

A traceroute between two datacenters comes back as six lines. Each one is a precise statement about what a multisite EVPN-VXLAN fabric does to a packet: the anycast gateway, the VXLAN wrap and unwrap, numbered versus unnumbered routers, the crossing between sites. All six, decoded on the boxes.

7 min read

Full NOC architecture, supervisor to three specialists to tools

What We Built: A Read-Only Agentic NOC, Step by Step

Part 5 of the Agentic NOC series. Three read-only MCP servers over a live fabric, firewall pair, and cluster; three A2A specialists and a supervisor; a local-first planner; one guarded write path; an autonomous monitor. The one design law, and how to rebuild it.

8 min read

juniper vjunos 26.2 on amd containerlab: what actually breaks

Juniper vJunos 26.2 on an AMD containerlab Host: What Actually Breaks

vJunos on containerlab is routine on Intel. On an AMD EPYC host the stock image refuses to start its nested VM, and the first test topology most people write hides a second failure that looks like AMD and is not. What breaks, what current vrnetlab already fixes, all reproduced on an EPYC 9575F.

8 min read

juniper vjunos 26.2 on amd eve-ng: fix the templates

Juniper vJunos 26.2 on an AMD EVE-NG Server: Fix the Image and the Templates

Put the vJunos 26.2 images on an AMD EPYC box running EVE-NG: the switch and router power themselves off, patch that and they hang at mount root, and Evolved on the default AMD template never starts QEMU. Four small edits in two places, each reproduced on the EPYC, every command ready to copy.

8 min read

Convergence of ACP and A2A into a single node

How MCP, A2A, and ACP Evolved and Converged

Part 4 of the Agentic NOC series. A cited timeline: MCP won the vertical axis in a year, A2A won the horizontal axis with a hundred-company tent, and ACP converged into A2A under the Linux Foundation rather than fragmenting the field. Why building on MCP plus A2A today is the safe bet.

5 min read

The A2A horizontal link between two agents with an Agent Card

Build a Minimal A2A Agent, With the Agent Card on the Wire

Part 3 of the Agentic NOC series. The smallest real A2A agent: one skill, an Agent Card served at the well-known URL, and the actual message/send JSON-RPC captured live. The horizontal axis, one agent discovering and delegating to another, built from scratch, and how it composes with MCP.

7 min read

The MCP vertical link from an agent down to a tool server

Build a Minimal MCP Server, With the JSON-RPC on the Wire

Part 2 of the Agentic NOC series. The smallest real MCP server: one read-only tool, stdio transport, and the actual JSON-RPC handshake captured from a live run. Reproducible with one dependency. This is the vertical axis, an agent reaching a tool, built from scratch.

6 min read

GoBGP anycast controller: a host decides which datacenter, the fabric forwards

GoBGP as a Host-Based Anycast Controller

Anycast usually lets the network decide which datacenter answers. I moved that decision onto two GoBGP hosts that watch both datacenters and steer a single global VIP between them. Here's the design, the traffic flow, and three failover drills that came through with zero failed requests.

6 min read

Subscribe to LevelUp I.T. newsletter and stay updated.

Don't miss anything. Get all the latest posts delivered straight to your inbox. It's free!