Evpn

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. ...