yesterday i got a chance to look at this again. I installed Rancher on my laptop (in a different subnet because it was on wfi), updated the cluster_registration_url and harvester was able to register ok.
When i tried Rancher on Harvester, they were both running in the same 192.168.20.0/24 subnet. Is there a limitation that i can not setup a vlan network on harvester that overlaps with it management subnet ?