Underlay Network Design with Contrail Cloud
Figure 1 provides a general guidance of what the underlay network fabric design looks like in a spine-and-leaf topology in order to cater to the cluster build-out as described in Cluster Design Overview.
As a requirement for RHOS, the RHOS Platform controller hosts must be on the same subnet, and thereby all controller hosts must be on the same rack in an Layer 3 Clos fabric underlay design.
Juniper recommends running the spine-and-leaf topology in a simple Open Shortest Path First (OSPF) area 0 Layer 3 Clos fabric design. The MX480 SDN gateways are connected separately to an additional top-of-rack (ToRs) leaf. This is similar to the Contrail Cloud Reference Architecture (CCRA) 1.0 underlay design.
 | Note: Due to limitations with Red Hat OpenStack Director (RHOSP 10) provisioning constructs, the Layer 3 Clos fabric underlay design is not supported. The multi-rack design is available only on Layer 2 fabric architecture. |
Figure 1: Underlay Network Fabric
