ipSpace.net Blog Posts

Labbing Network Technology Details with netlab

SwiNOG 40: Reliability of High-Speed Transceivers

netlab 25.09: IPv6 RA, Link Impairments, and Performance Gains

How Many Lab Devices Can netlab Handle?

SwiNOG 40: Submarine Cables

Netlab: The Fastest Way to Build Network Labs

iBGP Local-AS Route Propagation

Network Automation Reality Check with William Collins

SwiNOG 40: Application-Based Source Routing with SRv6

EVPN Designs: Layer-3 Inter-AS Option A

When Switches Flood LLDP Traffic

ArubaCX Decides When You're Done Changing a BGP Routing Policy

Configuring BGP Community Propagation is Confusing

SwiNOG 40: Trustworthy Network Automation

Fun Reading: AI: Great Expectations

BGP Community Propagation on Cisco IOS/XE: The 90's Called

MUST READ: Storage Devices and Latency

Fun Reading: Who is LLM?

ArubaCX: When BGP Soft Reconfiguration Becomes a No-Op

Ultra Ethernet: Reinventing X.25

Always Check Your Tests Against Faulty Inputs

Cisco IOS/XE Hates Redistributed Static IPv6 Routes

netlab 25.07: Summaries and Confederations

Dual-Stack Common-Services VRF Confuses Aruba CX

Worth Reading: The Secret Rules of the Terminal

Expanding a Running Netlab Topology

Worth Reading: Expert Generalists

Molly-Guard: a Lifesaver on a Ubuntu Server

IS-IS 3-Way Handshake and the Power of SHOULD

Start netlab Tools without Changing Topology File

SwiNOG 40: A Day of Awesomeness

Testing OSPF Device Configurations

Quality of OSPFv2 NSSA Implementations

Static Routes in netlab Lab Topologies

Network Digital Twins: Between PowerPoint and Reality

Dear Vendors, EVPN Route Attributes Matter

Public Videos: Whole IPv6 Curriculum

netlab 25.06: Fixing Nokia SR-OS Configuration Templates

Finding Source Routing Paths

ArubaCX Cannot Count When Dealing with VXLAN

netlab 2.0: Routers, Hosts, Gateways and Bridges

Interesting: Juniper MX and Jumbo Frames

Publishing Content as an Introvert

Finding End-to-End Paths: Topology and Endpoints

Weird: Ports on Linux Bridge Are Stuck

Where Are the NETCONF/YANG Tools?

Interesting: Bootstrapping HTTPS

Cumulus Linux (As We Know It) Is Gone

Multi-Layer Switching and Tunneling

Dear ArubaCX, VXLAN VNI Has 24 Bits

Worth Reading: Practical Advice for Engineers

ChatGPT Strikes Again: IS-IS on Unnumbered Interfaces 🤦‍♂️

Repost: On the Advantages of XML

Video: netlab Introduction by Ethan Banks

Response: True Unnumbered Interfaces

Amazing Speed of Bug Fixes in Nokia SR Linux

netlab 2.0: Use Custom Bridges on Multi-Access Links

Vibe Coding netlab Lab Topology with ChatGPT

Response: CLI Is an API

netlab 2.0.0: Hosts, Bridges, and SRv6

Forwarding Packets Across a Network

Screen Scraping in 2025

OSPF Loop Prevention with Area Range Summary LSAs

OSPF Summary LSA Loop Prevention

Breaking APIs or Data Models Is a Cardinal Sin

ChatGPT on OSPF Area Ranges and Summary LSAs

Switching, Routing, and Bridging Terminology

Worth Reading: BGP Unnumbered in 2025

How ARP Killed a Static Route

Rant: You Should Have Written a Book

netlab: Execute a Command on Multiple Devices

Response: Peer-to-Peer Communication in IPv6 World

Response: NAT Traversal Mess

iBGP Local-AS Next Hop Requirements

Transitioning into Networking, 2025 Edition

ARP Challenges in EVPN/VXLAN Symmetric IRB

Comparing IP and CLNP: Local (Node) Multihoming

Worth Reading: Why Quantum Crypto is Bollocks

Passive BGP Sessions

Response: Any-to-Any Connectivity in the Internet

Worth Reading: On Writing

netlab 1.9.6: Static Routes to Default Gateways

IPv6 and the Revenge of the Stupid Bridges

Routed Interfaces on Layer-3 Switches and Internal VLANs

Comparing IP and CLNP: Network State Summarization

Worth Reading: Standards for ANSI Escape Codes

Arista EOS Spooky Action at a Distance

Lab: IS-IS Designated Router Election

The Linux Bridge MTU Hell

Worth Reading: Traffic Steering into LSPs

netlab 1.9.5: New Cumulus Linux(NVUE) and Junos Features

Comparing IP and CLNP: Reaching Off-Subnet Nodes

Capturing Traffic in Virtual Networking Labs

Podcast: The Rise of NAT

Worth Reading: The Generative AI Con

Worth Reading: The IPv6 Agnostic Blog

Stub Networks in Virtual Labs

Worth Reading: Network Traffic Telemetry Protocols

Run BGP Across a Firewall

Worth Reading: Using SDN Controller with RSVP/TE

Goodbye, Cumulus Community Vagrant Boxes

BalticNOG Meeting (September 2025)

Limit the Scope of Git Diff

Projects to Work On – the AI Recommendations

Point-to-Point Links in Virtual Labs

Tagged VLAN 1 In a Trunk Is a Really Bad Idea

Lab: Passive IS-IS Interfaces

Group Similar Links in netlab Topologies

Please Wait While We're Preparing Your Interfaces

Arista cEOS Containers Run on Apple Silicon

Links in Virtual Labs

netlab 1.9.4: Bug fixes, VRRPv3 on Junos

The Curious Case of the BGP Connect State

Cisco Modeling Labs and Infrastructure-as-Code

Worth Reading: Drunken Plagiarists

Cisco VRRPv3 IPv6 Configuration Sucks

Use BGP Outbound Route Filters (ORF) for IP Prefixes

Sturgeon's Law, VRRPv3 Edition

The Ethernet/802.1 Protocol Stack

IBGP Is the Better EBGP

Concise Link Descriptions in netlab Topologies

Lab: Level-1 and Level-2 IS-IS Routing

Comparing IGP and BGP Data Center Convergence

Weird Junos IS-IS Metrics

netlab: Multi-Site VLANs

New IPv6 Documentation Prefix

netlab 1.9.3: MLAG, Static Routes, Node Cloning

Configuring IP Addresses Won't Make You an Expert

OSPFv3 on Bird Needs IPv6 LLA on the Loopback Interface

Happy Holidays and All the Best in 2025!

Worth Reading: Hard Truths about AI-assisted Coding

Use Disaggregated BGP Prefixes to Influence Inbound Internet Traffic

Video: Internet Routing Security (DEEP 2023)

IBGP Source Interface Selection Still Requires Configuration

Netlab Is Four Years Old

Worth Reading: Codespaces for Network Engineers

Is BGP PIC Edge an Oxymoron?

netlab: Sample Cisco ASAv Topology

Example: Multi-AS netlab Topology

Lab: Dual-Stack IS-IS Routing

IPv6 Support for Multiple Routers and Multiple Interfaces

EVPN Designs: EVPN IBGP over IPv4 EBGP

Dynamic BGP Peers

Lab: Using IS-IS Metrics

Latency Numbers Every Programmer Should Know

Using a BGP Route Server in an Internet Exchange Point

Running Routing Protocols over Tunnels

netlab 1.9.2: STP, LAG, Cisco IOL, Edgeshark

Worth Reading: Creating a Tech Blog

DEEP: a Boutique Security Conference

EVPN Designs: EVPN EBGP over IPv4 EBGP

netlab: How do I Specify VLAN Interface Parameters

How Does Netlab Deal with Server Reboots?

Per-Prefix and Per-VRF MPLS/VPN and EVPN Labels/VNIs

Lab: Configure IS-IS on Point-to-Point Links

NOG.HR: A NOG Meeting Worth Attending

Comparing IP and CLNP: Finding Adjacent Nodes

MUST READ: Egress Peer Engineering

Using BGP NO_EXPORT Community to Filter Transit Routes

Packet Pushers: Chat with Eric Chou

IS-IS Labs: Explore IS-IS Data Structures

EVPN Designs: EBGP Everywhere

netlab 1.9.1: Packet Capture, Routing Improvements

BGP Labs: Improvements (September 2024)

IS-IS Labs: Configure IS-IS Routing for IPv4

SR Linux Containers Run on Apple Silicon

One-Arm Hub-and-Spoke VPN with MPLS/VPN

IBGP Load Balancing with BGP Link Bandwidth

IPv6: Instructions for Use

Custom netlab Reports

EVPN Hub-and-Spoke Layer-3 VPN

Hub-and-Spoke VPN on a Single PE-Router

Hub-and-Spoke VPN Topology

New Project: IS-IS Hands-On Labs

EVPN Designs: Scaling IBGP with Route Reflectors

Routing Table and BGP RIB on SR Linux

Repost: Why Are Layer-2 VPNs So Popular?

Worth Exploring: Free, OpenSource IPv6 Textbook

Worth Exploring: Open-Source Network Automation Labs

Common Services VRF with EVPN Control Plane

Multivendor EVPN Just Works

Repost: The Benefits of SRv6

Using No-Export Community to Filter Transit Routes

Using Multiple Transit VNIs per EVPN VRF

Testing bgpipe with netlab

netlab 1.9.0: Routing Policies, Default Routes, Route Redistribution

BGP Session and Address Family Parameters

Arista cEOS Got Working MPLS Data Plane

Layer-3-Only EVPN: Behind the Scenes

Response: The Usability of VXLAN

Building Layer-3-Only EVPN Lab

Migrating a Data Center Fabric to VXLAN

Interesting: Crafting Endless AS Paths in BGP

Fun Reading: AI and Google’s Quarterly Results

Using netlab Reports

BGP, EVPN, VXLAN, or SRv6?

MUST READ: Making Segment Routing User-Friendly

CCIE Preparation with netlab

Worth Reading: AI Is Still a Delusion

EBGP Load Balancing with BGP Link Bandwidth

Worth Reading: GitHub Copilot Workspace Review

Worth Reading: Why Do We Have Native VLANs?

Again: What Exactly Is MPLS?

Worth Reading: Terminal Line Editing

BGP Labs: a Year Later

blog.ipspace.net Is On Cloudflare Pages

MUST READ: ChatGPT Is Bullshit

Master New Platforms and Technologies with netlab

Running Arista cEOS in GitHub Codespaces

Netlab Examples in GitHub Codespaces

Worth Reading: The Evolution of Network Security

Worth Reading: Don't Use Excel as a Source of Truth

Explore and Fix BGP Wedgies

Looking for a Simple Multihop EBGP Use Case

Running BGP Labs in GitHub Codespaces

netlab 1.8.4: vrnetlab Containers, Catalyst 8000v

Worth Reading: You Probably Don't Need AI

Automated Validation of BGP Labs

netlab 1.8.3: RIPv2, BGP Route Servers

Worth Reading: Cisco SD-Access and IoT Devices

The Mythical Use Cases: Traffic Engineering for Data Center Backups

Worth Reading: Not Just Scale

Worth Exploring: Infrahub by Opsmill

Worth Reading: ChatGPT Does Not Summarize

BGP Labs: Graceful Shutdown

Must Read: Make Two Trips

BGP Route Reflectors Considered Harmful

Testing Device Configuration Templates

Worth Reading: Using AWS Services via IPv6

EVPN Designs: IBGP Full Mesh Between Leaf Switches

EVPN Rerouting After LAG Member Failures

BGP Labs: Load Balancing across EBGP Paths

Testing Network Automation Data Transformation

Must Read: OSPF Protocol Analysis (RFC 1245)

MLAG Deep Dive: LAG Member Failures in VXLAN Fabrics

netlab 1.8.2: Bug Fixes, Usability Improvements

netlab: VRF Instantiation on Lab Devices

BGP Labs: Reduce FIB Size on Access Routers

MLAG Deep Dive: Dealing with LAG Member Failures

Worth Exploring: LibreQoS

Repost: State of Lisp Implementations (2024)

Famous Last Words: I'm Too Stupid for That

Worth Reading: Cisco vPC in VXLAN/EVPN Networks

BGP Labs: EBGP Sessions over IPv6 LLA Interfaces

Repost: The Real LISP Mobility Use Case

netlab: Global and Node VRFs

Worth Reading: Comparing GNS3, containerlab, and netlab

Repost: Think About the 99% of the Users

Stop the Network-Based Application Recognition Nonsense

Presentation: Introduction to netlab

Repost: Campus-Wide Wireless Roaming with EVPN

Worth Reading: Data Protection for Dummies

FRRouting Loopback Interfaces and OSPF Costs

Unintended Consequences of IPv6 SLAAC

Explore: Why No IPv6? (IPv6 SaaS)

LISP vs EVPN: Mobility in Campus Networks

Stateful Firewall Cluster High Availability Theater

SR/MPLS Security Framework

netlab 1.8.1: VRF OSPFv3, Integration Tests

Worth Reading: Cybersecurity Is Broken

Why Are We Using EVPN Instead of SPB or TRILL?

BGP Challenge: Build BGP-Free MPLS Core Network

EVPN Designs: VXLAN Leaf-and-Spine Fabric

Using wemulate with netlab

Repost: EBGP-Mostly Service Provider Network

BGP Labs: Advertise the Default Route

FRRouting Claims IBGP Loopbacks Are Inaccessible

OSI Layers in Routing Protocols

netlab: Building Leaf-and-Spine Fabrics with the Fabric Plugin

Worth Reading: Things We Know about Network Queues

BGP Labs: Stop the Fat-Finger Incidents

FRRouting RIB and FIB

Interface EBGP Sessions on Arista EOS

Running netlab and BGP Labs on Apple Silicon

Worth Reading: History of Ethernet

Video: Intro to Real Life Network Automation

Data Center Fabric Designs: Size Matters

BGP AS Numbers for a Private MPLS/VPN Backbone

OSPF Summarization and Split Areas

Cyber Crane Mesh Topology Built with netlab

Worth Reading: Talent Gap in IT

Worth Exploring: PCAP Analysis with Generative AI

BGP Labs: Limit the Number of Accepted BGP Prefixes

Multiline Expressions in Ansible Playbooks

Rant: Multi-Vendor EVPN Fabrics

netlab 1.8.0: Control-Plane Daemons, BIRD, dnsmasq

Worth Reading: Unbloating the Buffers

netlab on Packet Pushers

BGP Labs: Policy Templates

DHCP Relaying on a Linux Host

VXLAN Virtual Labs Have Never Been Easier

Ansible Set Operations Do Not Preserve List Order

Worth Reading: Popular git config options

BGP Labs: Remove Private AS from AS-Path

Implementing 'Undo' Functionality in Network Automation

Applying BGP Policy Templates

Network Layer: Interface or Node Addresses

BGP Labs: Session Templates

Can We Skip the Network Layer?

Removing FRRouting Configuration Is Not Idempotent

BGP Labs: Use Multiple AS Numbers on the Same Router

Precedence of Ansible Extra Variables

BGP Labs: Override Neighbor AS Number in AS Path

Availability Zones in VMware NSX-Based Cloud

Podcast: Network Automation Source(s) of Truth

BGP Labs: Work with FRR and Cumulus Linux

BGP Graceful Restart Considered Harmful

Is It The End, Or Can You Do Something in 2024?

netlab 1.7.1: Eye Candy

Registration No Longer Needed to Download Free PDFs

BGP Labs: Reuse BGP AS Number Across Sites

On Routing Protocol Metrics

Upcoming BGP Labs, 2024 Edition

Public Cloud Networking Hands-On Exercises

Goodbye, ipSpace.net Subscription

End-of-Year Cleanup: OSPF Blog Posts

Setting Source IP Address on Traffic Started by a Multihomed Host

BGP Challenge: Merge Autonomous Systems

Review: Unnumbered Interfaces in netlab

Worth Reading: The AI Supply Paradox

Worth Reading: State-of-the-Art AI

Video: Language Model Basics

netlab: Version-Specific Topology Files

BGP Labs: Use BGP Communities in a Routing Policy

Interviewing a Network Engineer Using a Single Scenario

Response: Vendor Network Automation Tools

Worth Reading: Network CI and Open Source

Worth Exploring: SRv6 Test Topologies

Video: netlab IP Address Management (IPAM)

AMS-IX Outage: Layer-2 Strikes Again

BGP Labs: Use BGP Route Reflectors

netlab 1.7.0: Lab Validation, Fabrics, BGP Nerd Knobs

The BGP Origin Attribute

Worth Reading: DNS over IPv6

Worth Reading: Use of HTTPS DNS Resource Records

The BGP Multi-Exit Discriminator (MED) Saga

BGP Labs: Set BGP Communities on Outgoing Updates

Can a Router Use the Default Route to Reach BGP Next Hops?

Worth Reading: Network Automation with GitHub Actions

Worth Reading: Going CCNP Emeritus

Video: Language Models in AI/ML Landscape

BGP Labs: AS-Path Prepending

Why Do We Need BGP Identifiers?

Is BGP TTL Security Any Good?

VXLAN/EVPN Layer-3 Handoff (L3Out) on Arista EOS

Video: Outages Caused by Bugs in BGP Implementations

Worth Reading: Cloudflare Control Plane Outage

BGP Labs: Using Multi-Exit Discriminator (MED)

Is Anyone Using netlab on Windows?

LAN Data Link Layer Addressing

Git Rebase: What Can Go Wrong?

Video: Kubernetes Calico Plugin

BGP Labs: Using BGP Local Preference

Open BGP Daemons: There's So Many of Them

Rapid Progress in BGP Route Origin Validation

Fibre Channel Addressing

Worth Reading: Confusing Git Terminology

Video: Hacking BGP for Fun and Profit

BGP Labs: Build a Transit Network with IBGP

Worth Reading: Taming the BGP Reconfiguration Transients

Weird: vJunos Evolved 23.2R1.5 Declines DHCP Address

Worth Exploring: BGP from Theory to Practice

Early Data-Link Layer Addressing

BGP Labs: Multivendor External Routers

netlab 1.6.4: Support for Multi-Lab Projects; More BGP Goodies

Video: History of BGP Route Leaks

BGP Labs: Build Larger Networks with IBGP

Will Network Devices Reject BGP Sessions from Unknown Sources?

Worth Reading: AI Risks

BGP Labs: TCP-AO Protection of BGP Sessions

netlab 1.6.3: BGP Nerd Knobs

Worth Reading: Some Thoughts on Digital Twins

Worth Reading: Introduction of EVPN at DE-CIX

Video: What Is Software-Defined Data Center

netlab 1.6.2: More Reporting Goodies

BGP Labs: Route Aggregation

What Is Ultra Ethernet All About?

BGP Session Security: Be Very Skeptical

Worth Reading: Flow Distribution Across ECMP Paths

Worth Reading: Single-Port LAGs

How GitHub Saved My Day

BGP Labs: Use BFD to Speed Up Convergence

Why Do We Need Source IP Addresses in IP Headers?

Does EVPN/VXLAN over SD-WAN Make Sense?

Repost: L2 Is Bad

BGP Labs: Protect EBGP Sessions

Addresses in a Networking Stack

Names, Addresses, and Routes

Dataplane MAC Learning with EVPN

Worth Reading: Where Are the Self-Driving Cars?

BGP Labs: Bidirectional Route Redistribution

DHCP Relaying Across a Firewall

OSPF ECMP with Unnumbered IPv4 Interfaces

Reliable ECMP with Static Routing

Case Study: BGP Routing Policy

Layer-3 WAN Handoff (L3Out) in VXLAN/EVPN Fabrics

Random Thoughts on Zero-Trust Architecture

BGP Labs: Simple Routing Policy Tools

Lifetime ipSpace.net Subscription

OSPF and ARP on Unnumbered IPv4 Interfaces

ARP and Static Routes

Worth Reading: Looking Inside Large Language Models

ARP Details Behind the Scenes

BGP Labs: The Basics

How GitHub Learned How Hard Distributed Systems Are

Engagement Farming

netlab 1.6.1: BGP Reports, Markdown Support

Getting Comfortable with the Command Line

Free Subscription No Longer Needed to Watch the ipSpace.net Videos

Worth Reading: Networking for AI Workloads

New Project: BGP Hands-On Labs

netlab 1.6.0: New Commands, Reports, and External Connectivity

Worth Reading: MP-TCP in Hybrid Access Networks

Worth Reading: Eyes Like Saucers

Multipath TCP (MPTCP) Resources

Configuring Linux Traffic Control in a Sane Way

Fun Reading: History of the Early Internet

Worth Watching: Ethernet Thick Yellow Cable

Worth Reading: Another BGP Session Reset Bug

Worth Reading: AI Does Not Help Programmers

Worth Reading: What Is Going on With BGP?

Worth Reading: Always the Same Warning Signs

Summer Break 2023

Use FRR Containers to Learn Routing Protocol Fundamentals

When a Device Without an IP Address Wants to Play the IP Game

Exercise: Fix BGP Route Leaks

Worth Reading: Some Blogging Myths

Worth Reading: A Primer on Communication Fundamentals

Please Respond: MANRS Customer Survey

EIGRP Stub Routers

Classification of BGP Route Leaks (RFC 7908)

netlab Release 1.5.4: New Junos Platforms

Worth Reading: Building Stuff with Large Language Models Is Hard

Spoofing ICMP Redirects for Fun and Profit

Video: SD-WAN Security

Are LACP Fast Timers Any Good?

Distributed Systems Resources

EIGRP Third-Party Next Hops

Default EBGP Policy (RFC 8212)

Worth Reading: Internet WAN Edge Design

Worth Reading: Unbounded TCP Memory Usage

Video: Link State Routing Protocol Implementations

Source IP Address in Multicast Packets

NTP in a Nutshell

Path Failure Detection on Multi-Homed Servers

Goodbye Twitter. It Was Fun While It Lasted

Worth Reading: Cargo Cult AI

Worth Reading: Building Trustworthy AI

Network Security Vulnerabilities: the Root Causes

Inter-VRF DHCP Relaying with Redundant DHCP Servers

Dealing with Cisco ACI Quirks

Simplify netlab Topologies with Link Groups

Worth Reading: Trapped by Technology Fallacies

Why Is Source Address Validation Still a Problem?

Video: Types of Switching ASICs

Find the Optimal Level of Automation Abstraction

New: Disaster Recovery Resources

ITNOG 7 Wrap-up

netlab Release 1.5.3: libvirt Public Networks

Worth Reading: Official Ansible Collection for SR Linux

Service Insertion with BGP FlowSpec

Video: Kubernetes Container Networking Interface (CNI)

MLAG Clusters without a Physical Peer Link

Is ChatGPT an Efficiency Multiplier?

Modifying BGP Behavior with xBGP API

Building a DMVPN Test Lab with netlab

MUST READ: End-to-End Arguments in System Design

Worth Reading: IPv6 Deployment Status

Video: 400GbE Optics

Silent Hosts in EVPN Fabrics

Small Site EBGP-Only Design

netlab Release 1.5.2: Aruba CX, External Tools, Tunnel Interfaces

Interesting: BGP Zombie Outbreak on Juniper Routers

CloudFlare: From IP packets to HTTP

Advantages and Drawbacks of EVPN-based Multihoming

Why Is OSPF (and BGP) More Complex than STP?

Is Dynamic MAC Learning Better Than EVPN?

IPv6 Security in Layer-2 Firewalls

Use Existing (DMVPN) Device Configurations in netlab

Systems Design: What We Hope We Know

180 Gbps Software-Only Linux Router

Video: SD-WAN CPE Architecture

Multi-Vendor EVPN Fabrics

New: Network Infrastructure as Code Resources

IPv6 Addressing on Point-to-Point Links

Using VLAN and VRF Links in netlab Topologies

ChatGPT Explaining the Need for iSCSI CRC

Worth Reading: Was MPLS TE Worth the Effort?

Video: netlab Topology File

Building a Small Network with ChatGPT

Should I Care About RPKI and Internet Routing Security?

DHCP Relaying with Redundant DHCP Servers

Turning WiFi into a Thick Yellow Cable

Kicking the Tires of GitHub Copilot

New: High Availability Clusters in Networking

netlab Release 1.5.1: VLAN and VRF Links

DHCP Relaying in EVPN VRFs

Worth Reading: The Death of CLI

Video: Sample Kubernetes SDN Implementations

ChatGPT on BGP Routing Security

Studying EVPN to Prepare for a Job Interview

What Happened to Leaf Switches with Four Uplinks?

DHCP Relaying in VXLAN Segments

Worth Reading: Off-Path Firewall with Traffic Engineering

Worth Reading: The Dangers of Knowing Everything

Video: Chassis Switch Architectures

Will ChatGPT Replace Stack Overflow?

New: CI/CD in Networking Resource Page

External Links on Spine Switches

Test VRF-Aware DHCP Relaying with netlab

Worth Reading: History of 8-bit Bytes

Worth Exploring: OSPF Watcher

Video: vPC Fabric Peering with EVPN Multihoming

Advantages of Using Generalized TTL Security Mechanism (GTSM) with EBGP

First Steps in IPv6 Deployments

Leaf-and-Spine Fabrics Between Theory and Reality

Test DHCP Relaying with netlab

Worth Reading: Putting Large Language Models in Context

Worth Reading: The War on Expertise

Video: SD-WAN Backend Architecture

DHCP Relaying Details

New: Anycast Resource Page

Dynamic MAC Learning: Hardware or CPU Activity?

netlab: Change Stub Networks into Loopbacks

Video: Getting Started with netlab

History of IP TTL in EBGP Sessions

Feedback: Microsoft Azure Networking

Alternatives to IBGP within Multihomed Sites

Suspending Devices in netlab Labs

Video: Packet Buffers in Data Center ASICs

How Many Spines Should a Leaf-and-Spine Fabric Have?

Measuring Virtual Network Device Boot Times

Some Operations Are Not Worth Automating

Start Multiple netlab Labs on the Same Server

Worth Reading: On ChatGPT

Video: Link State Routing Protocol Basics

Feedback: Designing Active/Active and Disaster Recovery Data Centers

CE-to-CE IBGP Session in a Multihomed Site

MUST READ: Machine Learning for Network and Cloud Engineers

Start Large netlab Topologies in Smaller Batches

Video: Kubernetes SDN Architecture

Real-Life Not-Exactly-Networking AI Use Case

Response: Nothing Works (in Enterprise IT)

Improve BGP Startup Time on Cisco IOS

Mix Containers and VMs with netlab Release 1.5.0

Worth Reading: 2 Mpps on a Pentium CPU

Video: Migrating into a Cloud

IRB Models: Edge Routing

Response: Complexities of Network Automation

Design Clinic: Small-Site IPv6 Multihoming

netlab Release 1.5.0: Larger Lab Topologies

Worth Reading: A Debugging Manifesto

MUST READ: Nothing Works

Built.fm Podcast with David Gee

Hiding Malicious Packets Behind LLC SNAP Header

Response: Network Automation Expert Beginners

Will DPUs Change the Network?

netlab: Building a Layer-2 Fabric

Worth Reading: Do We Need Network Automation

Worth Exploring: OMNI and AERO

Video: 2023 Network Engineer Path to Success

Relationships between Layer-2 (VLAN) and Layer-3 (Subnet) Segments

Feedback: Docker Networking Deep Dive

Network Automation Expert Beginners

netlab Release 1.4.3: Cisco IOS XRv, MPLS on FRR

Worth Reading: Routing Protocol Implementation Evaluation

Lack of Use Cases: a Lesson about Handling Hype

Video: MLAG with EVPN Deep Dive

State of LDPv6 and 6PE

Updates: AWS Networking

Is It Time to Replace TCP in Data Centers?

netlab Release 1.4.2: Juniper vMX and Junos Features

Happy Holidays and All the Best in 2023!

A Quick Look at AWS Scalable Reliable Datagram Protocol

DPU Hype Considered Harmful

vagrant-libvirt Dependency Hell

Worth Reading: NetOps Requires AI/ML and Rules

Worth Reading: Fail-Slow at Scale

Video: IPv6 Traffic Filtering Details

Arista EOS Configuration Automation

Why Would You Need an Overlay Network?

Running Routing Protocols over MLAG Links

netlab: VRF Lite over VXLAN Transport

Worth Reading: Egress Anycast in Cloudflare Network

Video: What Can Netlab Do?

Are DPUs Any Good?

ICMP Redirects and Suboptimal Routing

Azure Networking Update Is Completed

netlab Release 1.4.1: Cisco ASAv

Congestion Control Algorithms Are Not Fair

Worth Reading: Troubleshooting EVPN Control Plane

Video: Cloud Infrastructure-as-Code

Azure Networking Update (Phase 1)

Integrated Routing and Bridging (IRB) Design Models

Network Automation: a Service Provider Perspective

netlab: IRB with Anycast Gateways

Worth Reading: Resolverless DNS

Worth Reading: Another Hugo-Based Blog

Video: Exposing Kubernetes Services to External Clients

Multihoming Cannot Be Solved within a Network

BGP in ipSpace.net Design Clinic

BGP Unnumbered Duct Tape

netlab VXLAN Router-on-a-Stick Example

Worth Reading: History of Fiber Optics Cables

Video: Routing Protocols Overview

BGP Route Reflectors in the Forwarding Path

Using EVPN/VXLAN with MLAG Clusters

SRv6 as a Host-to-Host Overlay

netlab Release 1.4.0: EVPN Asymmetric IRB, Anycast Gateways, VRRP

Must Read: Routing Will Never Be a Solved Problem

Video: EVPN Multihoming Deep Dive

Rant: Cloudy Snowflakes

Scalability Aspects of SR-MPLS

Worth Exploring: NetTowel

Could I Use netlab instead of GNS3?

Leave BGP Next Hops Unchanged on Reflected Routes

History of Ethernet Encapsulations

Network Automation Considered Harmful

Use VRFs for VXLAN-Enabled VLANs

Video: EVPN Multihoming Taxonomy and Overview

New Webinar: Internet Routing Security

Why Do We Need IBGP Full Mesh?

On Applicability of MPLS Segment Routing (SR-MPLS)

netlab Router-on-a-Stick Example

netlab Release 1.3.3: Bug Fixes

EVPN VLAN-Aware Bundle Service

OSPF External Routes (Type-5 LSA) Mysteries

Cumulus Linux NVUE: an Incomplete Data Model

netlab Release 1.3.2: Mikrotik RouterOS 7, Additional EVPN Platforms

Worth Reading: VXLAN Drops Large Packets

Video: Traffic Filtering in the Age of IPv6

More Arista EOS BGP Route Reflector Woes

EVPN/MPLS Bridging Forwarding Model

Repost: What's Wrong with Network Automation

netlab EVPN/VXLAN Bridging Example

Worth Reading: QUIC Is Not a TCP Replacement

Worth Reading: EVPN/VXLAN with FRR on Linux Hosts

Video: Kubernetes Services Types

Cumulus Linux Network Command Line Utility (NCLU)

Combining MLAG Clusters with VXLAN Fabric

Repost: On the Viability of EVPN

netlab VXLAN Bridging Example

Worth Reading: The Hierarchy Is Bullshit

Video: Cloud-Native Environments

SR-MPLS or SRv6 for Greenfield Networks

Linux Networking Data Plane Configuration

EVPN/VXLAN or Bridged Data Center Fabric?

netlab Release 1.3.1: BGP local-as, FRR and Cumulus Data Plane Enhancements

The Basics of Network Address Translation (NAT)

Multi-Cloud: Myths and Reality

VLAN Interfaces and Subinterfaces

Infrastructure-as-Code Sounds Scary

netlab: VRF Lite Topology with VLAN Trunks

Worth Exploring: NetDoc – Automated Network Discovery and Documentation

Fun Times: Is Cisco ACI Dead?

Video: Testing IPv6 RA Guard

From Bits to Application Data

How Routers Became Bridges

Was IPv6 Really the Worst Decision Ever?

netlab Release 1.3: VXLAN and EVPN

Feedback Appreciated: Next-Generation Metro Area Networks

Worth Reading: Latency Matters When Migrating Workloads

Video: Kubernetes Services Overview

Router Interfaces and Switch Ports

netsim-tools Renamed to netlab

Twilight Zone: File Transfer Never Completes

Worth Exploring: Akvorado Flow Collector and Visualizer

Twilight Zone: File Transfer Causes Link Drop

Worth Reading: On the Dangers of Cryptocurrencies...

Repost: Buffers, Congestion, Jitter, and Shapers

Worth Reading: Smart Highways or Smart Cars?

netlab VLAN Module Is Complete

MLAG Deep Dive: Layer-3 Forwarding

VXLAN-to-VXLAN Bridging in DCI Environments

Help Appreciated: netsim-tools Device Features

Worth Reading: Is IPv6 Faster Than IPv4?

Video: IPv6 RA Guard and Extension Headers

MLAG Deep Dive: Layer-2 Flooding

Beware of Vendors Bringing White Papers

When You Find Yourself on Mount Stupid

netlab: Combining VLANs with VRFs

Video: Rogue IPv6 RA Challenges

Using Custom Vagrant Boxes with netlab

Select the Best Switching ASIC For the Job

MLAG Deep Dive: Dynamic MAC Learning

netlab VLAN Trunk Example

Video: Network Address Scopes

Data Center Switching ASICs Tradeoffs

MLAG Deep Dive: System Overview

VXLAN-Focused Design Clinic in June 2022

netlab Simple VLAN Example

Worth Reading: ACI Terraform Scalability

Worth Reading: Automation Report From 1958

Video: Ugly Challenges of Using AI/ML in Networking

Worth Reading: Resolverless DNS

ipSpace.net Blog Is in a Public GitHub Repository

Simplify and Standardize Mantra Encounters Reality

Largest netlab Topology I've Seen So Far

Video: Typical Kubernetes Inter-Pod Traffic Walk

Is OpenFlow Still Kicking?

SDN Controller Taxonomy

Ethernet Encryptor Market Overview (2022 Edition)

Networking Hardware/Software Disaggregation in 2022

Worth Reading: Using LEO and GEO Satellite Internet

Video: Network Address Assignments

Is Fibre Channel Still a Thing?

New in netlab: VLANs, Hardware Labs, VRF Loopbacks

IPv6 Unique Local Addresses (ULA) Made Useless

Living with Small Forwarding Tables

Worth Reading: The State of fq_codel (and Bufferbloat)

Worth Watching: Source Routing on the Edge (iNOG::14v)

Video: Practical Aspects of IPv6 Security

Configure Hardware Labs with netlab

Modern IBGP Design with AddPath and ORR

What Happened to FabricPath and Its Friends?

Video: The Long Tail of AI/ML Problems

Creating MPLS/VPN Labs With netlab

Is X.25 Still Alive?

Detecting Byzantine Link Failures with SNMP

netlab Multi-Platform Custom Configuration Templates

OMG: Hop-by-Hop Path MTU Discovery

Video: Understanding Kubernetes Pods

New in netlab: More MPLS and VRFs, Dell OS10, Cumulus 5.0 on Containerlab

Network Digital Twins Work Best in PowerPoint

Everything Is Better with a GUI (even netlab)

Worth Reading: New Linux Command Line Tools

Video: Challenges of Managed SD-WAN Services

Telephone System Is a Bad Example of Hierarchical Addresses

AWS Automatic EC2 Instance Recovery

Keep Blogging, Some of Us Still Read

Creating VRF Lite Labs With netlab

Worth Reading: Full-Stack Network Automation

Worth Reading: The AI Illusion

Video: IPv6 Trust Model

Next Hops of BGP Routes Reflected by Arista EOS

Opinion: Do You Care about MPLS in 2022?

BGP Labeled Unicast Interoperability Challenges

netlab MPLS Support

Worth Reading: Higher Levels of Address Aggregation

Worth Reading: Career Advice I'd Give to Younger Me

Video: Combining Data-Link- and Network Layer Addresses

Is MPLS/VPN Too Complex?

Duplicate ARP Replies with Anycast Gateways

BGP Labeled Unicast on Arista EOS

Combining BGP and IGP in an Enterprise Network

Worth Reading: VMware Operations Guide

Draw a Network Diagram from Excel Spreadsheet

Video: Managed SD-WAN Services

Beware: Ansible Reorders List Values in Loops

BGP Labeled Unicast on Cisco IOS

MPLS/LDP Creation Myths

Automating NSX-T Deployments

Video: Kubernetes Networking Model

So-Called Modern VPNs: Marketing and Reality

Hub-and-Spoke VPLS: Revenge of LDP

netsim-tools Release 1.1.4

Feedback: Ansible for Networking Engineers

Worth Reading: Switching the Technology Stack

Video: Functions-as-a-Service Demo

Should We Use LISP?

Segment Routing vs LDP in Hub-and-Spoke Networks

Flow-Based Packet Forwarding

netsim-tools Release 1.1.3

Worth Reading: Misconceptions about Route Origin Validation

Worth Reading: AI Makes Animists of Us All

Video: Comparing TCP/IP and CLNP

Data Plane Quirks in Virtual Network Devices

Contribute to netlab: OSPFv3

Repost: LISP Is a False Economy

Running a Ubuntu VM on a Mac M1

Video: Use Cases for AI/ML in Networking

Cache-Based Packet Forwarding

New netlab Installation Instructions

ICMP Redirects Considered Harmful

Feedback: DMVPN Webinars

Using netlab with containerlab: Welcome to the World of Tomorrow

Worth Reading: Performance Testing of Commercial BGP Stacks

netsim-tools (now netlab) on the Modem Podcast

The Impact of Jumbo Maximum Frame Size on Data Center Switches

Running BGP between Virtual Machines and Data Center Fabric

Feedback: Cisco ACI Webinars

Packet Forwarding 101: Header Lookups

Worth Reading: End-to-end Congestion Control Cannot Avoid Latency Spikes

Worth Reading: Crazy about VMware SD-WAN

Video: Network Layer Addressing

Build Vagrant Boxes for Your Network Devices

OMG: VTP Is Insecure

Mixed Feelings about BGP Route Reflector Cluster ID

Feedback: ipSpace.net Materials

Worth Reading: We're a Decade Past Blade Server Market Peak

Worth Reading: Non-Standard Standards, SRv6 Edition

Lesson Learned: The Way Forward

Do a Cleanup Before Automating Your Network

netsim-tools Release 1.1.2

BGP Route Reflector Myths

Sample Lab: SR-MPLS on Junos and SR Linux

Worth Reading: The Network Does Too Much

Worth Exploring: Christoph Jaggi's New Web Site

Video: Kubernetes Architecture

MTU Settings in Virtual Network Devices

Three Dimensions of BGP Address Family Nerd Knobs

More: Hardware Differences between Routers and Switches

Sample Lab: RSVP TE on Junos

Video: Machine Learning Techniques

Introducing netlab Plugins

Layer-3 Carrier Ethernet

Running IS-IS over Unnumbered Ethernet Interfaces

Video: Local Area Network Addressing

Feedback: Recursive BGP Next Hop Resolution

Just Out: netsim-tools Release 1.1

Running OSPF over Unnumbered Ethernet Interfaces

Worth Reading: Free Software Is a Gift

Video: Cloud Services Hierarchy

Feedback: Cisco ACI Deep Dive

Recursive BGP Next Hops: an RFC 4271 Quirk

Microsegmentation Terminology

netsim-tools: New in December 2021

That's It for 2021

Highlights: Dynamic Negotiation of BGP Capabilities

Checking Network Device Configurations in a GitOps CI Pipeline

Running Network Automation Tools in a Container

Worth Reading: Snowflake Network Devices

Podcast: Ironing Out the BGP Ruffles

Response: Hardware Differences between Routers and Switches

What Are You Going to Test in Network Automation CI/CD Pipeline?

Highlights: Multi-Threaded Routing Daemons

Building a BGP Anycast Lab

Worth Reading: Xen on AWS Nitro NICs

Video: Machine Learning 101

Optimal BGP Path Selection with BGP Additional Paths

Scalable Policy Routing

Dynamic Negotiation of BGP Capabilities

Mikrotik RouterOS and VyOS Added to netsim-tools

Git as a Source of Truth for Network Automation

Worth Reading: Load Balancing on Network Devices

Lesson Learned: Some Services Are Not Worth Delivering

Circular Dependencies, VMware NSX-T Edition

Anycast Fundamentals

Multi-Threaded Routing Daemons

netlab Custom Groups and Deployment Templates

RFC 9098: Operational Implications of IPv6 Extension Headers

Worth Reading: How to Get Useful Answers to Your Questions

Video: Early Data-Link-Layer Addressing

Hardware Differences between Routers and Switches

Anycast Works Just Fine with MPLS/LDP

Optimizing the Time-to-First-Byte

Overlay Virtual Networking Examples

Jerikan+Ansible: a Configuration Management System

Interesting: What's Wrong with Bitcoin

Non-Stop Routing (NSR) 101

Building a Separate Infrastructure for Guest Access

Creating BGP Multipath Lab with netlab

Feedback: Business Aspects of Networking

Managing Hierarchical Device Configurations

Soap Opera: SRv6 Is Insecure

Video: How Can You Master Public Cloud Networking?

Why Does Internet Keep Breaking?

Even Simple Data Models Are a Huge Win

Where Would You Need DNS Anycast?

netsim-tools Release 1.0

Worth Reading: Operators and the IETF

Worth Reading: Programming Sucks

Nonlinear Effects of Optimization-Induced Complexity

Big Picture: BFD, Non-Stop Forwarding, and Graceful Restart

EVPN/VXLAN Complexity

Interactions Between BFD and Graceful Restart

Feedback: How Networks Really Work

Worth Reading: Making a Case for Automation Architecture

Worth Reading: Network Validation Evolution at Hostinger

Video: Introduction to AI/ML Hype

Circular Dependencies Considered Harmful

Do We Need Multiple Global IPv6 Addresses Per Interface (RFC 7934)

Graceful Restart and BFD

Start a Virtual Lab with a Single Command

Worth Reading: The Software Industry IS STILL the Problem

MUST READ: ARP Problems in EVPN

Lessons Learned: Complexity Will Kill Your System

BGP Optimal Route Reflection 101

Why Does DHCPv6 Matter?

Graceful Restart and Routing Protocol Convergence

New Content in AWS Networking Webinar

OMG: Democratizing Network Automation

Must Read: BGP Private AS Range

Video: Theoretical View of Network Addressing

Should You Build or Buy a Router?

Worth Reading: Do We Need Segment Routing?

Graceful Restart and Other Control Plane Protocols

Feedback: Mastering Cloud Networking

Video: Public Cloud Networking Is Different

Reusing Underlay Network for Infrastructure Services

Watch Out: ISR Performance License

Graceful Restart (GR) 101

State of IT Security in 2021

Worth Reading: Breaking Down Silos

Building a Small Data Center Fabric with Four Switches

IS-IS Flooding Details

Another SD-WAN Security SNAFU: SQL Injections in Cisco SD-WAN Admin Interface

netlab Network Topology Graphs

Interesting Concept: Time Dilation

LSA/LSP Flooding in OSPF and IS-IS

New: ipSpace.net Design Clinic

Stateful Switchover (SSO) 101

Configuring NSX-T Firewall with a CI/CD Pipeline

Worth Reading: Ops Questions in Software Engineering Interviews

Lessons Learned: Fundamentals Haven't Changed

netlab Overview

Open-Source DMVPN Alternatives

Non-Stop Forwarding (NSF) 101

Comparing Forwarding Performance of Data Center Switches

Video: Introduction to Network Addressing

Automating NSX-T Firewall Configuration

netlab Python Package and Unified CLI

Worth Reading: A Historical Perspective On The Usage Of IP Version 9

Worth Reading: Simplifying Networks

MUST Read: Operational Security Considerations for IPv6 Networks (RFC 9099)

netsim-tools Release 0.8.1: Cumulus VX and Nokia SR Linux Containers

OpenFlow Realities, 2021 Edition

Quantum Computing and OpenFlow

Designing Networks: From Tricycles to Aircraft Carriers

Thank You for Everything Irena, We'll Miss You Badly

Webinars in the First Half of 2021

Worth Reading: Blog About What You've Struggled With

Worth Reading: How to Miss a Deadline

Video: Typical Large-Scale Bridging Use Cases

Stretched VLANs: What Problem Are You Trying to Solve?

Why Do We Need BGP-LS?

Unexpected Interactions Between OSPF and BGP

Comparing EVPN with Flood-and-Learn Fabrics

Worth Reading: Machine Learning Deserves Better Than This

Worth Reading: Is Your Consultant a Parasite?

Video: Comparing Routing and Bridging

Questions about BGP in the Data Center (with a Whiff of SRv6)

Deploying Plug-and-Pray Software in Large-Scale Networks

OSPF Inter-Process Route Selection

ipSpace.net Subscription for System Administrators

Intricate AWS IPv6 Direct Connect Challenges

Worth Reading: The Lost Designer

Lessons Learned: Technology Still Matters

Unnumbered Ethernet Interfaces, DHCP Edition

Real-Life Network-as-a-Graph Examples

Unequal-Cost Multipath with BGP DMZ Link Bandwidth

Feedback: Azure Networking

Worth Reading: The Neuroscience of Busyness

Worth Reading: Switching to IP fabrics

Video: Cisco SD-WAN Policy Design

Routing Protocols: Use the Best Tool for the Job

Unnumbered Ethernet Interfaces

Single-Metric Unequal-Cost Multipathing Is Hard

netsim-tools release 0.7: Cumulus VX, EIGRP, and BGP IPv6 AF

Worth Reading: Azure Datacenter Switch Failures

Worth Reading: Running BGP in Large-Scale Data Centers

Video: Kubernetes Principles

Local TCP Anycast Is Really Hard

Packet Forwarding and Routing over Unnumbered Interfaces

Mythbusting: NFV Data Center Fabric Buffering Requirements

Feedback: Kubernetes Networking Deep Dive

Worth Watching: Rethinking BGP in the Data Center

Worth Exploring: Working with Linux VRFs

Video: We Still Need Networking in Public Clouds

Automation: Dealing with Vendor-Specific Configuration Keywords

Back to Basics: Unnumbered IPv4 Interfaces

Packet Bursts in Data Center Fabrics

netsim-tools release 0.6.2

Worth Reading: Rethinking Internet Backbone Architectures

Video: Cisco SD-WAN Site Design

Does Small Packet Forwarding Performance Matter in Data Center Switches?

Back to Basics: The History of IP Interface Addresses

BGP-Free MPLS Core with Segment Routing

Response: There's No Recipe for Success

Worth Reading: When Stretching Layer Two, Separate Your Fate

Worth Reading: My Secret Startup Past

Video: IP Routing Fundamentals

Real-Life: How to Start Your Automation Journey

Back to Basics: Do We Need Interface Addresses?

Segment Routing Segment IDs and MPLS Labels

Feedback: Microsoft Azure Networking

RFC 7868: The Definitive EIGRP Guide

Blogging Rule#1: Own Your Content

netsim-tools Release 0.6: BGP, IS-IS, SR-MPLS, FRR

MUST READ: Deploy AWS Security Rules in a GitOps World with Terraform, GitLab CI, Slack, and Python

Everything Is a Graph

Worth Reading: Understand Your Single Points of Failure

Worth Reading: The Insider's Guide To Evangelizing Good Design

Interview: What New Technologies Should You Aim to Master?

Microsoft Azure: Remember Exchange Server?

Response: Is Switching Latency Relevant?

Using Unequal-Cost Multipath to Cope with Leaf-and-Spine Fabric Failures

Starting Network Automation for Non-Programmers

Worth Reading: Get Better at Programming by Learning How Things Work

MUST READ: Machine Learning is a Marvelously Executed Scam

Video: Transparent Bridging Fundamentals

Fundamentals: Is Switching Latency Relevant?

Netsim-tools Release 0.5 Work with Containerlab

Must Read: Automate Nexus-OS Fabric Deployment

Start Automating Public Cloud Deployments with Infrastructure-as-Code

Worth Reading: Fail-Fast is Failing... Fast

Worth Reading: Data Manipulation in Jinja2

Bringing New Engineers into Networking on Software Gone Wild

Claim: You Don't Have to Be a Networking Expert to Do Kubernetes Network Security

Reader Question: What Networking Blogs Would You Recommend?

Free Exercise: Build Network Automation Lab

Building Unnumbered Ethernet Lab with netlab

Video: Why Do We Need Kubernetes?

Planning the Extended Coffee Break: Three Months Later

Intermittent Terraform Authentication Failure Using AWS Provider in a Vagrant VM

Dealing with Cloud Challenges

netsim-tools: Unnumbered Interfaces, Configuration Modules, OSPF

Worth Reading: Learning without Burnout

Worth Reading: Network Automation ChatBot with Discord

Interview: Will AI Replace the Networking Engineers?

Relative Speed of Public Cloud Orchestration Systems

Hands-On: Azure Route Server

Unequal-Cost Multipath in Link State Protocols

There's No Recipe for Success

Worth Reading: Splitting the Ping

Interview: Is Networking Dead?

Public Cloud Behind-the-Scenes Magic

Repost: Using MP-TCP to Utilize Unequal Links

Using YAML Instead of Excel in Network Automation Solutions

Azure Route Server: Behind the Scenes

Worth Reading: Modules, Monoliths, and Microservices

Video: Cisco SD-WAN Routing Design

Topology- and Congestion-Driven Load Balancing

Azure Route Server: The Challenge

Interesting Tool: Schema Enforcer

Learning Networking Fundamentals at University?

Appreciating the Networking Fundamentals

Grasp the Fundamentals before Spreading Opinions

On the Usability of OSI Layered Networking Model

You Must Understand the Fundamentals to Be Successful