# Lesson 5: OCI Networking Services

> Virtual Cloud Network, Gateways, Peering, VCN Security, Load Balancer

## Virtual Cloud Network (VCN)

* A private network in Software layer which lives in an OCI Region.
* Enables OCI resources to securely communicate with **Internet**, other **instances** or **on-premises(内部, 本地) data center**.
* Highly Available, Scalable and Secure.

### How to establish a VCN

* Private address pool assigned to a VCN
* Subnets in private address pool

![](https://imgur.com/pZME7IM.png)

## Gateways

### Internet Gateway

It provides a path for network traffic between your **VCN** and the **internet**.

### Nat Gateway

It gives cloud resources without public IP addresses access to the internet without exposing those resources to incoming internet connections. 它提供的云资源无需公共IP地址即可访问Internet，而不会将这些资源暴露于传入的Internet连接中。

### Dynamic Routing Gateway (DRG)

when connecting your existing on-premises network to your virtual cloud network (VCN).

![](https://imgur.com/6B9z5Nl.png)

There are 2 mechanisms of DRG:

* VPN Connect (IPSec VPN)

  An **encrypted connection over the internet** between between your on-premises network (a data center or corporate LAN) and your Oracle virtual cloud network (VCN)
* FastConnect

  An **dedicated, private connection** between your data center and Oracle Cloud Infrastructure, **bypasses the internet** (绕过internet)

### Service Gateway

which lets resources in VCN access public services such as **Object Storage**, but **without** using an internet or NAT gateway. So your traffic is not going over the internet

![](https://imgur.com/PBSsDP7.png)

## VCN Security

* Firewall rules to protect subnets
* Network Security Group consists of set of rules applied only for VNICs

## Peering

**communicate to other VCNs**, it has 2 types of peering:

* Local VCN peering

  Connect 2 VCNs in the **same region** so that their resources can communicate using private IP addresses.

  ![](https://imgur.com/t4tCxes.png)
* Remote VCN peering

  Connect 2 VCNS in **different regions** so that their resources can communicate using private IP addresses.

  ![](https://imgur.com/FToNNM8.png)

## Load Balancer

It provides automated traffic distribution from one entry point to multiple servers reachable from your virtual cloud network (VCN) A load balancer improves **resource utilization**, facilitates **scaling**, **fault tolerance** and helps ensure **high availability**. You can configure multiple load balancing policies and application-specific **health checks** to ensure that the load balancer directs traffic only to healthy instances.

It has 2 types of LB:

* Public Load Balancer

  To accept traffic from the internet, you create a public load balancer. ![](https://imgur.com/hIQJLW5.png)
* Private Load Balancer

  To isolate your load balancer from the internet and simplify your security posture 处境