DO I need any ELB (Load Balancer) to network between private subnets ? - AWS

Question

here is the example I want to ask

this following brief shapes of architecture

    □          <-------->               □           <---------->            □
    ↓                ↓                  ↓                 ↓                 ↓   

private subnet----- networking(A)----- private subnet ----- networking(C) ------ private subnet

following considering conditions

• total 4 subnets: 1 public subnet / 3 private subnets
• the brief architecture omitted public part only shows private subnets part
• already I got 1 Load balancer on the internet facing area in public subnet already
• I got 3 private subnets in VPC
• I want to make them network send and request packets between private subnets

I want to ask you

according to above pretenses,

there is already internet facing load balancer

but at this point

I want to ask you

Q. 1 Do I need "additional" Load balancers to communicate and build network between private subnets?

especially

Q. 2 Do I have to put Load balancer inbetween private subnets which is pointing "network A section" or "network C section"?

Q. 2' DO I need to put Load balancer in networking A section or networking C section to build network with each other? (sending http packets, communicate, build network)

Answer 1

You don't need a load balancer to facilitate communication between subnets. You need to have routes defined in route table associated with the subnet. Usually you will see a routes similar to 10.0.0.1/16 => local where the 10.0.0.1/16 is the CIDR of the VPC. Local route allows to communicate with in the VPC. So The subnet can communicate with other subnets with in the VPC. So all you need is a local route.

A load balancer is used for a completely different reason. An example scenario would be, when you have a multiple web server instances that serves the http web traffic, You can add a load balancer in front of the instances to distribute the traffic between the instances. You can prevent single server from getting overloaded by using a load balancer and distribute the load to multiple servers.