The new cage in codfw cannot support direct layer-2 adjacency to our LVS servers, meaning we can only support services behind LVS there which use IPIP encapsulation.
Background
The new switches for {T380240} were ordered without the VXLAN license for Juniper, and the cage will be a hybrid of Juniper/Nokia (due to needing the racks online sooner than we would be able to support a full Nokia setup). This rules out using VXLAN for layer-2 extension in the new cage.
That decision was made after discussions at the SRE Summit which suggested that by the time the racks went live we would no longer have any services dependent on the layer-2 connectivity from LVS load-balancers. But we are not quite there so day-one we need to avoid placing some hosts in the new location.
Hostname List
The main hosts we need to avoid racking in the new cage for now are the Kubernetes hosts (work to move them to IPIP is tracked in T352956). Additionally some search hosts should be avoided (see T373020).
The full list of hostname prefixes we cannot rack in the new cage right away are:
aux-k8s-ctrl aux-k8s-worker cirrussearch dse-k8s-ctrl dse-k8s-worker elastic kubestage kubestagemaster ml-serve ml-serve-ctrl ml-staging ml-staging-ctrl wikikube-ctrl wikikube-worker