Thank you for posting this in Microsoft Q&A.
Yes, as you mentioned the key vault replication happens automatically. You do not have to enable any specific setting in key vault for replication.
The replication regions are already paired with another region. The contents of your key vault are replicated both within the region and to the paired region. The paired region is usually at least 150 miles away, but within the same geography. This approach ensures high durability of your keys and secrets.
If individual components within the key vault service fail, alternate components within the region step in to serve your request to make sure that there's no degradation of functionality. You don't need to take any action—the process happens automatically and will be transparent to you.
You can refer below article to know more about the replication on Key vault.
https://zcusa.951200.xyz/en-us/azure/key-vault/general/disaster-recovery-guidance
To know more about Azure paired regions you can refer below article,
https://zcusa.951200.xyz/en-us/azure/reliability/cross-region-replication-azure#azure-paired-regions
Let me know if you have any further questions.
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