Initial Setup Considerations for ACI Multi-Site

ACI Multi-site TEP Pool

“Note: The TEP pool prefixes used within each site do not need to be exchanged across sites to allow inter-site communication. Therefore, there are no technical restrictions regarding how those pools should be assigned.
However, the strong recommendation is not to assign overlapping TEP pools across separate sites so that your system is prepared for future functions that may require the exchange of TEP pool summary prefixes”.

This is the VLAN ID for all fabric connectivity. This VLAN ID should be allocated solely to ACI, and not used by any other legacy device in your network.
So, We can use the same Infra VLAN for both sites.

Reference: Cisco Community

IP address pool for bridge domain multicast address (GIPo).
For Cisco APIC in a Cisco ACI Multi-Site topology, this GIPo address can be the same across sites.
Valid range: 225.0.0.0/15 to 231.254.0.0/15, prefixlen must be 15 (128k IPs)

The APIC fabric ID in a Multi-Site deployment can be unique, or the same value can be used across sites for greenfield or brownfield deployments.

The only scenario where it is mandatory to deploy separate fabric IDs across sites is the deployment of shared GOLF (supported by Cisco ACI Release 3.1(1)), specifically when auto-RT is enabled and all the sites are part of the same BGP ASN. If those two conditions are not true, then it is perfectly fine to deploy the same fabric ID across all the sites even in a shared GOLF design.

The Cisco ACI Multi-Site site ID or site name must be unique across all sites. This parameter
is configured directly on the Cisco ACI Multi-Site Orchestrator and cannot be changed after it
has been assigned. To reconfigure the site ID, you will need to perform a clean wipe to return
to the factory defaults.
Note: The Cisco ACI Multi-Site ID is different from the Cisco ACI fabric ID assigned on the
APIC (Fabric ID can be the same on both sites).