- Update (20140124): OpenVswitch integration required for GRE SDN networking is currently broken in Apache CloudStack 4.2.x (and master branch) according to this.
CloudStack has two types of Zones – Basic zones and Advanced Zones.
A Basic zones is a flat network where SecurityGroups are used for traffic isolation while Advanced Zones can use VLAN, GRE or STT based isolation. The maximum VLANs possible per zone is 4096 while the actual number depends on the L3 switching device’s capabilities. Since every guest tenant is allocated one VLAN ID, the maximum tenants supported would be 4K tenants within the same zone. If there is a requirement to support more than 4K customers within the same zone, SDN technologies like GRE and STT can be used.