connect to Compute instance on Private Subnet using Public Load balancer OCI

 In this post, i am going to demonstrate on how we can connect to a VM Compute instance running on Private Subnet using a Network Load balancer. There are many ways available through which you can connect using Fast Connect, IPSec VPN or using Bastion Service which are beyond the scope for this post. The Oracle Cloud Infrastructure Flexible Network Load Balancing service (Network Load Balancer) provides automated traffic distribution from one entry point to multiple backend servers in your virtual cloud network (VCN). It operates at the connection level and load balances incoming client connections to healthy backend servers based on Layer 3/Layer 4 (IP protocol) data. The service offers a load balancer with your choice of a regional public or private IP address that is elastically scalable and scales up or down based on client traffic with no bandwidth configuration requirement.

Network Load Balancer provides the benefits of flow high availability, source and destination IP addresses, and port preservation. It is designed to handle volatile traffic patterns and millions of flows, offering high throughput while maintaining ultra low latency. Network load balancers have a default 1 million concurrent connection limit. Network Load Balancer is the ideal load balancing solution for latency sensitive workloads. For more information, you can refer to https://docs.oracle.com/enus/iaas/Content/NetworkLoadBalancer/overview.htm

Steps:- I have two subnets one is private and another one is public. The compute instance is created in Private Subnet and Network Load balancer is defined under Public subnet. Both the subnets have their respective Security lists and Route Tables. The compute instance will be accessible through SSH port 22.

Create a VCN

Create a NAT Gateway

Create  a Service gateway

Create Route Rule

Create a Security List 

192.168.0.8/30 is the CIDR for LB subnet

Create a Compute instance on private Subnet

Next, Create a the public Subnet which will host the LB.

Create the NSG for defining the ingress and egress of LB

Now Create the Network Load balancer

unselect Preserve Source IP

make Sure the health checks are passed

Now use the Public IP of the LB to connect to the private Compute instance using SSH

In this Blog Post, we looked into one of the easiest solution on how to connect to Compute instance running on Private Subnet. Using Network Load balancer, we can also connect to DB running on specific port, Windows RDP etc. I hope this post will help someone. Till then, enjoy learning Cloud.