Worked on the major/cloud-init repository to enhance network configuration reliability by implementing VLAN MAC address configuration. Developed a feature allowing users to set a MAC address for VLAN subinterfaces, addressing a regression where MAC addresses were not properly propagated to netplan. This update improved deployment stability and ensured consistent network interface behavior across cloud environments. The work involved Python development, cloud infrastructure expertise, and network configuration skills, with comprehensive updates to documentation and test coverage. By automating VLAN networking more reliably, the changes reduced post-deployment networking issues and contributed to more predictable cloud-init behavior for complex network setups.