What will Route53 do if client ip matches multiple CIDR blocks in different CIDR Locations?

Question

I haven't found behavior of Routing policy IP-based that a client ip matches 2 or more CIDR blocks in different CIDR Locations.

**For an example**, domain: abc.com

| Record Name | Routing Policy | CIDR Location | Entry Value |
| --- | --- | --- | --- |
| geo.abc.com | IP-based | CIDR-Location-1 | 198.51.100.1 |
| geo.abc.com | IP-based | CIDR-Location-2 | 198.51.100.2 |

and we have 2 CIDR Locations in CIDR Collection

| CIDR Location | CIDR Blocks |
| --- | --- |
| CIDR-Location-1 | 1.1.1.0/24 |
| CIDR-Location-2 | 1.1.0.0/16 |

**Question**: When the client (ip 1.1.1.1) trys to resolve geo.abc.com, what result will he get?

Answer

I see you added more input/clarification.
Here is what I tested:
- 2 separate VPC in us-east-1 (one with 10.1.0.0/16 and the other with 10.1.1.0/24) 
- Created a Private hosted zone and associated with the 2 VPC above.
- Spun 2 hosts in each of the VPC with manual assigned IP (.10)
 - nslookup and response was served in round robin, sometime getting the same IP.

Answer

Not sure what you meant by: "**CIDR-Location-1 contains CIDR Block 1.1.1.0/24 CIDR-Location-1 contains CIDR Block 1.1.0.0/16**"
You will just have 1.1.0.0/16 spanning your VPC, so...

As for **"Record 1: geo.abc.com, CIDR-Location-1, A record to 198.51.100.1 Record 2: geo.abc.com, CIDR-Location-2, A record to 198.51.100.2**"
You configure your DNS with multiple A records for the same FQDN - the requests would get served in round-robin.

Record Name	Routing Policy	CIDR Location	Entry Value
geo.abc.com	IP-based	CIDR-Location-1	198.51.100.1
geo.abc.com	IP-based	CIDR-Location-2	198.51.100.2

What will Route53 do if client ip matches multiple CIDR blocks in different CIDR Locations?

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