Evpn

After rebuilding my Arista SR-MPLS lab on Containerlab, I wanted to keep that same workflow and move into Cumulus EVPN-VXLAN. This time the goal was not just to recreate a fabric, but to get hands-on quickly with a repeatable topology, fast verification, and a workflow that fits naturally with automation and AI. Why I built this lab My earlier Containerlab work focused on Arista SR-MPLS. That exercise proved something important: once the topology, startup configs, and validation flow are written as code, the time from idea to working lab drops dramatically. ...

After moving my blog to https://garywong.pro, this is my first technical article under the new branding. Instead of migrating the old post 1:1, I rebuilt the entire SR-MPLS lab from scratch — this time using Containerlab, version control, and documented architecture decisions. Why I rebuilt this lab I originally built this topology on EVE-NG back in 2023. It worked, but it also had typical issues: No version control Risk of silent config drift Hard to reproduce environments CLI screenshots instead of structured notes On Containerlab, things changed: Topology as YAML (Infrastructure as Code) All configs tracked in GitHub Topology image embedded in README Fast teardown / rebuild cycle This is closer to how real network testing should be done in 2026. ...

In previous posts, I discussed the construction of an EVPN-VXLAN fabric using Cisco NDFC. A critical aspect often overlooked — and the focus of this post — is the transition from a traditional 3-tier data centre architecture to an EVPN-VXLAN setup. One notable challenge in this transition is the configuration of the DHCP relay. Why DHCP Relay Behaves Differently in EVPN-VXLAN Traditionally, DHCP relays are configured to identify the default gateway using link-selection (DHCP Option 82 sub-option 5), ensuring IP addresses are allocated from the correct scope. ...