Hello Nicolas
OK I understand. So by design, your initial “underlay” network is such that there are parts of the network that can’t communicate directly. So you have multiple MPLS service providers, and you have a particular site that is connected to two (or more) MPLS networks that acts as the “hub” for communication between entities in those MPLS networks.
So if you have topology where two vEdge devices cannot communicate directly over the underlay due to the restrictions you describe, but can each communicate with the main site where the controllers are hosted, the Cisco SD-WAN fabric will inherently handle the situation to a certain extent. The system’s OMP and TLOC properties will play a role in determining viable paths.
If direct communication between two vEdges is not possible due to underlay restrictions, the tunnel establishment will fail. However, even if a direct path isn’t available, the vEdge devices are aware (thanks to OMP and TLOC information) of other vEdges they can communicate with. In your scenario, both restricted vEdges can communicate with the main site. Thus, when they need to exchange data, the traffic will inherently use the main site as a relay point since a direct path isn’t viable. This is part of the SD-WAN’s inherent path decision mechanism.
So based on the OMP path attributes, the vEdge will choose the best available path. If the direct path is unavailable, it will select another path, like through the main site.
I hope this has been helpful!
Laz