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I haven't changed my vpc/subnet settings since making an aws account, and I've recently found my rds instance is apparently in 3 subnets (subnet is listed as default with 3 subnet names underneath), one of which also has my application server. Is it necessary to have my rds in all 3 subnets? I want to move it to a separate subnet away from the application server and make it private - if that's the case is there anything in particular I will need to do?

user11508332
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1 Answers1

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Typically, an Amazon RDS instance is running on one server in one subnet.

However, when launching the database, you are asked to provide a Subnet Group, which identifies which subnets the database could launch in. These are typically private subnets within the VPC.

If you are using a Multi-AZ database, then it will use two subnets -- one for the Master (running) database and one for the secondary (standby) database.

It is also possible to create Read Replicas that could be in a different subnet to the Master database.

Bottom line: You are probably viewing the list of subnets in the Subnet Group that it can use, but it is likely to only be in one subnet at the moment.

John Rotenstein
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    right, how would I go about telling which subnet my instance is actually in? – user11508332 Feb 13 '20 at 12:13
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    Mmm, it seems that it doesn't outright say which subnet is being used. However, the RDS db instance will show an Availability Zone. You can use this information to determine which Subnet is being used (on the assumption that you have a maximum of one subnet per AZ, which is normally the situation). You can also nominate the AZ when the db instance is launched. – John Rotenstein Feb 13 '20 at 23:11
  • Go to your database, then look at Connectivity & Security > Networking > Availability Zone @user11508332 – Shad Oct 19 '22 at 03:06