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Five parts in, the network is complete and nothing is plugged into it. Part 5 gave the fabric a front door; this part gives it tenants. Seven Ubuntu VMs get built from one golden image, land on the leaf pairs with LACP bonds, and pick up addresses in the role-based subnets from Part 1. It is the least glamorous part of the series and the one where two invisible details, a missing link speed and a VLAN that must match on both switch peers, decide whether anything works at all.
One image, one file per node
The build philosophy: bake everything shared into one image, keep per-node identity down to a single file. The base is an Ubuntu 24.04 cloud image seeded once with cloud-init at bake time, users, SSH keys, packages, and two small extras you will meet below, and then cloud-init is disabled so clones boot fast and never re-provision. Every node in the lab, masters, workers, and the services node, is a copy-on-write clone of that image (Part 2's overlay trick doing its job).
Per-node identity is exactly one netplan file. Everything the node needs to be itself, its bond, its fabric address, its DNS, sits in seventeen lines:
Three lines in that file connect backward through the series. The default route points at 10.110.0.1, the anycast gateway that Part 4 configured on every leaf pair, so the node's gateway is always one hop away no matter where it lands. The first nameserver is the services node that Part 9 will build into the lab's DNS. And the bond's MAC is pinned, because a bond that changes MAC across reboots makes switches relearn and DHCP reservations lie. One honest note: the nodes run the default MTU of 1500 while the fabric runs 9216; the fabric's jumbo headroom exists to absorb VXLAN overhead and future tuning, not because the hosts need jumbo today.
