Welcome to OCI, my name is Sergio Castro. Today we'll see introduction to virtual cloud networking. Let's get started. Our objectives today are regions, availability domains, fault domains, of course VCN, Virtual Cloud Network, and subnets. A region is our virtual data center, or your virtual data center, it's a physical datacenter that is close to you. We have north of 26 regions across the world, one located close to you. Each region has availability domains, one or more availability domains. You can leverage these availability domains for your high availability, continuous operations, business continuity of your resources, your infrastructure that you build within OCI and each one of the availability domains have fault domains of their own. If you are in a region that only has one availability domain, you still have the fault domains for you to isolate your resources in a way that you have continuity of your business. You have high availability of your operations. Now let's go ahead and see the virtual cloud network. You have your subnets that you can configure them to be public, private. You can communicate outside of the virtual cloud network to your on-premise resources like your customer datacenter through the dynamic routing gateway or DRG. We have other gateways, so you can communicate to the Internet on a bidirectional communication via the internet gateway. You can also communicate on a one-way out to the Internet, but do not allow profit coming in through the NAT gateway. You have the service gateway that will allow you to communicate to object storage or the autonomous database. Those are public-facing resources within OCI, and it doesn't make sense for you to go over the Internet, reach them, and then come back. You use the service gateway for that. Of course, the VCN comes with set of rules that you can configure. By default, everything's prohibited from reaching your virtual cloud network except for port 22 and for pinging ICMP. But you can always block them, and you can enable per need your resources. If you need to create a web server, you can open port 80. That's the security list or the Network Security Group. These are concepts that we'll see shortly. Also you have route tables that you need to set up in order to leverage one of these services, the Internet gateway, the NAT gateway, the dynamic routing gateway, the VCN resides at a single region. If you are in the Azure region, for example, you create a virtual cloud network that is valid and reachable only in that region. Each VCN, you can have one or more CIDR blocks of your choice. One VCN can have a 10.0.0.0 CIDR. Then you can add a second one, a 172.16.0.0, for example, and perfectly fine. You can have resources in each one of these CIDRs. A CIDR block can be modifying after the VCN is created. Now that we're talking about CIDR blocks, in the next segment, we're going to take a deeper dive into CIDR blocks. We'll go into explaining how they work and how the notation works, and how you can leverage them for your benefit of virtual cloud networking.
