Multi-Site Domain for VXLAN BGP EVPN Fabrics
A Multi-Site Domain (MSD) is a multifabric container that is created to manage multiple member fabrics. An MSD is a single point of control for definition of overlay networks and VRFs that are shared across member fabrics. When you move fabrics (that are designated to be part of the multifabric overlay network domain) under the MSD as member fabrics, the member fabrics share the networks and VRFs created at the MSD-level. This way, you can consistently provision network and VRFs for different fabrics, at one go. It significantly reduces the time and complexity involving multiple fabric provisionings.
As server networks and VRFs are shared across the member fabrics (as one stretched network), the new networks and VRFs provisioning function is provided at the MSD fabric level. Any new network and VRF creation is only allowed for the MSD. All member fabrics inherit any new network and VRF created for the MSD.
The topology view for the MSD fabric displays all member fabrics, and how they are connected to each other, in one view. You can deploy overlay networks (and VRFs) on member fabrics from a single topology deployment screen, instead of visiting each member fabric deployment screen separately and deploying.
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A few fabric-specific terms:
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Standalone fabric – A fabric that is not part of an MSD is referred as a standalone fabric from the MSD perspective. Before the MSD concept, all fabrics were considered standalone, though two or more such fabrics can be connected with each other.
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Member fabrics – Fabrics that are part of an MSD are called member fabrics or members. Create a standalone fabric (of the type Easy_Fabric) first and then move it within an MSD as a member fabric.
When a standalone fabric is added to the MSD, the following actions take place:
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The standalone fabric's relevant attributes and the network and VRF definitions are checked against that of the MSD. If there is a conflict, then the standalone fabric addition to the MSD fails. If there are no conflicts, then the standalone fabric becomes a member fabric for the MSD. If there is a conflict, the exact conflicts are logged in the pending errors log for the MSD fabric. You can remedy the conflicts and then attempt to add the standalone fabric to the MSD again.
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All the VRFs and networks definitions from the standalone fabric that do not have presence in the MSD are copied over to the MSD and in turn inherited to each of its other existing member fabrics.
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The VRFs and networks (and their definitions) from the MSD (such as the MSD's VRF, and L2 and L3 VNI parameters that do not have presence in the standalone fabric) are inherited into the standalone fabric that just became a member.
Fabric and Switch Instance Variables
While the MSD provisions a global range of network and VRF values, some parameters are fabric-specific and some parameters are switch-specific. The parameters are called fabric instance and switch instance variables.
Fabric instance values can only be edited or updated in the fabric context from the VRFs and Networks window. Double click on the appropriate fabric to view Fabric Overview and choose Networks or VRFs tab. Some of the examples of fabric instance variables are BGP ASN, Multicast group per network or VRF, etc. For information about editing multicast group address, see Creating Networks in the MSD Fabric.
Switch instance values can be edited on deployment of the network on the switch. For example, VLAN ID.