Category: Tags
netlab
The netlab tool will help you be more proficient once you decide to drop GUI-based network simulators and build your labs using CLI and infrastructure-as-code principles.
You can also use netlab (potentially together with GitHub Codespaces) to build online, easy-to-consume, hands-on training solutions. I used that approach to build the BGP labs and IS-IS labs.
EVPN
ChatGPT trying (and failing) to explain EVPN
What Is EVPN?
Before going into the technical details, let’s start with the basics: What is EVPN, how does it work, and where can you use it?
- What Is EVPN?
- EVPN: The Great Unifying Theory of VPN Control Planes?
- EVPN Is More than VPLS on Steroids
- BGP, EVPN, VXLAN, or SRv6?
- Multivendor EVPN Just Works
- Why Are We Using EVPN Instead of SPB or TRILL?
- VXLAN Broadcast Domain Size Limitations
- Active-Active Data Centers with VXLAN and EVPN
- Comparing EVPN with Flood-and-Learn Fabrics
- Studying EVPN to Prepare for a Job Interview
- Is Dynamic MAC Learning Better Than EVPN?
- Dataplane MAC Learning with EVPN
EVPN Designs
EVPN was designed to be used in an IBGP environment on top of an IGP. With the eruption of EBGP as better IGP hype, many vendors tried to adapt EVPN to an environment running EBGP instead of OSPF. We covered some of the typical EVPN designs in these blog posts:
- BGP in EVPN-Based Data Center Fabrics
- Using EVPN in Very Small Data Center Fabrics
- Pragmatic EVPN Designs
- VXLAN Leaf-and-Spine Fabric
- IBGP Full Mesh Between Leaf Switches
- BGP Route Reflectors Considered Harmful
- Scaling IBGP with Route Reflectors
- EBGP Everywhere
- EVPN EBGP over IPv4 EBGP
- EVPN IBGP over IPv4 EBGP
Other blog posts focus on various design details:
- BGP in EVPN-Based Data Center Fabrics (Updated)
- Scaling EVPN BGP Routing Designs
- Implications of Valley-Free Routing in Data Center Fabrics
- VXLAN and EVPN on Hypervisor Hosts
- When EVPN EBGP Session between Loopbacks Makes Sense
- BGP AS Numbers on MLAG Members
- EVPN/VXLAN or Bridged Data Center Fabric?
- Multi-Vendor EVPN Fabrics
- Layer-3 WAN Handoff (L3Out) in VXLAN/EVPN Fabrics
- VXLAN/EVPN Layer-3 Handoff (L3Out) on Arista EOS
Finally, several blog posts describe various EVPN VPN topologies:
- Simple EVPN/VXLAN Bridging
- Building Layer-3-Only EVPN Lab
- Layer-3-Only EVPN: Behind the Scenes
- Common Services VRF with EVPN Control Plane
- Hub-and-Spoke VPN Topology
- EVPN Hub-and-Spoke Layer-3 VPN
EVPN Implementation Details
There are tons of tiny little things that can go wrong when you try to deploy EVPN. I documented them as I stumbled upon them:
- EVPN Route Target Considerations in EBGP Environment
- Using 4-Byte BGP AS Numbers With EVPN on Junos
- Dissecting IBGP+EBGP Junos Configuration
- Private VLANs With VXLAN
- VMware NSX Killed My EVPN Fabric
- EVPN Route Targets, Route Distinguishers, and VXLAN Network IDs
- EVPN Auto-Rd and Duplicate MAC Addresses
- Next-Hop and VTEP Reachability in EVPN Networks
- Duplicate ARP Replies with Anycast Gateways
- More Arista EOS BGP Route Reflector Woes
- Using EVPN/VXLAN with MLAG Clusters
- DHCP Relaying in EVPN VRFs
- Silent Hosts in EVPN Fabrics
- Repost: Campus-Wide Wireless Roaming with EVPN
- Using Multiple Transit VNIs per EVPN VRF
- ARP Challenges in EVPN/VXLAN Symmetric IRB
Beyond VXLAN
While EVPN is often used with VXLAN today, it was designed to work with the MPLS data plane, resulting in a few quirks:
- EVPN With MPLS Data Plane in Data Centers
- Q-in-Q Support in Multi-Site EVPN
- EVPN/MPLS Bridging Forwarding Model
- EVPN VLAN-Aware Bundle Service
- Does EVPN/VXLAN over SD-WAN Make Sense?
- Per-Prefix and Per-VRF MPLS/VPN and EVPN Labels/VNIs
EVPN Rants
Some vendors’ marketing engineers (or Senior Directors) can’t stand anyone telling them their implementation might be suboptimal, going to great lengths to prove to themselves they’re right, and generating beautiful fodder for rants.
- Don’t Sugarcoat the Challenges You Have
- The EVPN Dilemma
- The EVPN/EBGP Saga Continues
- EVPN Control Plane in Infrastructure Cloud Networking
- EVPN/VXLAN Complexity
- On the Viability of EVPN
- Multi-Vendor EVPN Fabrics
- LISP vs EVPN: Mobility in Campus Networks
Videos
You can watch numerous videos from the EVPN Technical Deep Dive webinar without an ipSpace.net account:
- EVPN Multihoming Taxonomy and Overview
- EVPN Multihoming Deep Dive
- MLAG with EVPN
- vPC Fabric Peering with EVPN Multihoming
- Advantages and Drawbacks of EVPN-based Multihoming
What Others Wrote About EVPN
- EVPN in Data Center
- Arista EVPN-Based Automation Virtual Lab
- Switching to IP fabrics
- ARP Problems in EVPN
- EVPN/VXLAN with FRR on Linux Hosts
- Troubleshooting EVPN Control Plane
- Introduction of EVPN at DE-CIX
Networking Fundamentals
I firmly believe that you cannot be a good networking engineer1 without a firm grasp of the networking fundamentals, and I couldn’t resist pointing that out a few times (see also certifications-related posts):
- You Must Understand the Fundamentals to Be Successful
- Learning Networking Fundamentals at University?
- Grasp the Fundamentals before Spreading Opinions
- Appreciating the Networking Fundamentals
- When You Find Yourself on Mount Stupid
Regardless of how far down this page you’ll get, these blog posts are a must-read:
- Management, Control, and Data Planes in Network Devices and Systems
- Relationships between Layer-2 (VLAN) and Layer-3 (Subnet) Segments
- On the Usability of OSI Layered Networking Model
I would also suggest exploring these series of blog posts as well as textbooks and other resources I collected:
- Interfaces and Ports
- Packet Forwarding Basics
- Integrated Routing and Bridging (IRB) Designs
- IP Anycast and Anycast Gateways
- Site and Host Multihoming
- High Availability Switching
- Fast Failover
- Unnumbered IPv4 Interfaces
- CLI versus API
- Network State Consistency
The rest of the fundamentals-related blog posts are collected on this page.
Network Addressing
Addresses and routes are the basic concepts anyone dealing with a network must (eventually) grasp. These blog posts describe how we got a hierarchy of addresses:
- Names, Addresses, and Routes
- Addresses in a Networking Stack
- Why Do We Need Source IP Addresses in IP Headers?
- Early Data-Link Layer Addressing
- Fibre Channel Addressing
- LAN Data Link Layer Addressing
- Can We Skip the Network Layer?
- Network Layer: Interface or Node Addresses
Deep Dives
These blog posts dive deeper into interesting topics:
- Why Is OSPF not Using TCP?
- Chasing CRC Errors in a Data Center Fabric
- IBGP, IGP Metrics, and Administrative Distances
- Is Switching Latency Relevant?
- Response: Is Switching Latency Relevant?
- Routing Protocols: Use the Best Tool for the Job
- From Bits to Application Data
- On Routing Protocol Metrics
- OSI Layers in Routing Protocols
If you like them, it’s probably time you start exploring the deep-dive series I already mentioned.
A Bit of a History
These blog posts might help you figure out some less obvious details or give you a historical perspective on why networking technologies evolved to where we are right now:
If you want to dive deeper into historical technologies, you might enjoy the comparison of TCP/IP and OSI (CLNP) protocol stacks:
- Finding Adjacent Nodes
- Reaching Off-Subnet Nodes
- Network State Summarization
- Local (Node) Multihoming
There Be Rants
Long-time readers know I can’t resist a good rant:
- Lies, damned lies and product marketing
- Bridges: a Kludge that Shouldn't Exist
- How Did We Ever Get Into This Switching Mess?
- Response: The OSI Model Is a Lie
- The World in Which IPv6 Was a Good Design
- IPv4, IPv6, and a Sudden Change in Attitude
- Was IPv6 Really the Worst Decision Ever?
Everything Is a Graph
You can represent every network as a graph of network devices (nodes) and links2. Rachel Traylor covered the graph theory in the (free) Network Connectivity, Graph Theory, and Reliable Network Design and Graph Algorithms in Networks webinars; these blog posts might provide some extra details:
Networking Fundamentals Videos
Finally, I published dozens of videos describing the networking concepts as part of the How Networks Really Work webinar that got at least some minor positive feedback. The videos describe:
Business aspects of networking technologies
Some people liked the non-technical take on networking I recorded in 2019 and 2020:
- Define the Problem Before Searching for a Solution
- Know Your Users' Needs
- Should You Build or Buy a Solution?
- High-Level Technology Guidelines
Fallacies of distributed computing
- Fallacies of Distributed Computing
- The Network Is Not Reliable
- End-to-End Latency Is Not Zero
- Bandwidth Is Neither Infinite Nor Cheap
- Networks Are (Not) Secure
- Internet Has More than One Administrator
- Networks Are Not Homogenous
Networking challenges and the importance of a layered approach
- Overview of Networking Challenges
- Introducing Transmission Technologies
- Beyond Two Nodes
- The Need for Network Layers
- Retransmissions and Flow Control in Computer Networks
- Putting the Networking Layers Together
- Breaking the End-to-End Principle
Network Addressing
- Introduction to Network Addressing
- Theoretical View of Network Addressing
- Early Data-Link-Layer Addressing
- Local Area Network Addressing
- Network Layer Addressing
- Comparing TCP/IP and CLNP
- Combining Data-Link- and Network Layer Addresses
- Network Address Assignments
- Network Address Scopes
- The Basics of Network Address Translation (NAT)
Switching, Routing, and Bridging
- Review Questions: Switching, Bridging and Routing
- What Are Bridging, Routing, and Switching?
- Getting a Packet Across a Network
- Multi-Layer Switching and Tunneling
- Finding Paths Across the Network
- Path Discovery in Transparent Bridging and Routing
- Transparent Bridging Fundamentals
- IP Routing Fundamentals
- Comparing Routing and Bridging
- Typical Large-Scale Bridging Use Cases
Routing Protocols
- Routing Protocols Overview
- Link State Routing Protocol Basics
- Link State Routing Protocol Implementations
Lessons Learned from 35 Years of Networking