Add external NLB as target group of ALB

Question

is it possible to add external facing NLB as target group of ALB? I am getting error

An error occurred (ValidationError) when calling the RegisterTargets operation: 
The IP address '54.xxx.xxx.xx' is not allowed,
as it must be an address from a VPC subnet, RFC1918, or RFC6598

while calling aws elbv2 register-targets API

Answer 1

It is possible to add NLB IP addresses as target group of ALB as long as NLB is internal and both are in same VPC or their VPCs are peered

Answer 2

That's not possible. NLBs can target ALBs. ALBs cannot target NLBs.

Answer 3

From your error I see uou are trying to add public ip as Target which not supported 100%.

You can only have rfc1918 range for this.