网络课程笔记

00:00 Hi.

00:00 So in this lecture let's understand the basic building blocks of the VPC.

00:06 You can also call them as core components of the VPC.

00:09 And then in the next section we are going to dive deep into the advanced concepts of the VPC.

00:15 So everything starts with AWS region.

00:18 So whenever you create a VPC first you have to select the region.

00:22 And every region comes with three or more availability zones depending on which region you are choosing.

00:29 Now here for simplicity, I'm just showing two AZS or availability zones.

00:34 Now you create a VPC and VPC sits into your AWS region.

00:39 Now whenever you create a VPC, the first thing that you have to do is to assign the IPv4 or IPv6 address

00:46 range.

00:47 And that's the IP address range for your VPC.

00:50 Now that address you assign in the form of Cidr notation also called as classless Inter-domain routing.

00:58 So for this VPC I am putting IPv4 address range, for example ten .0.0.0 slash 16, which gives me around

01:08 65,000 private IPv4 addresses for this VPC.

01:13 And in the next lecture, we are going to talk about how to calculate the Sidr and how to know how many

01:18 IP addresses you can have inside the VPC.

01:22 Right.

01:22 So once you have the VPC, the next thing you create is the subnet.

01:26 So you are dividing now a VPC address range into a smaller networks in the form of subnets.

01:33 And as you create the subnets you have to associate them with a particular availability zone.

01:39 So the scope of the subnet is at A-Z level.

01:42 And that's where when you launch any EC2 instance or any other resources which are AZ bound, you have

01:48 to launch inside a particular subnet.

01:51 For example, you are launching the EC2 machine either in subnet A or in a subnet B, so subnet is small

02:00 address range from within the VPC.

02:02 And again you assign the Cidr range for your subnets.

02:07 Now once you create the subnets of course you need to have the routing.

02:11 That means how the traffic flows across these subnets.

02:14 So whenever you create a VPC.

02:17 So AWS will automatically create a main route table which is applied to all these subnets.

02:23 And we are going to see what this main route table looks like and how to change the route table entries.

02:29 But many a times you would want that every subnet has their own routing mechanism.

02:35 For example some subnet has the workload which are exposed to the internet.

02:39 Some subnets host the database machines which need not be exposed to the internet.

02:44 So you might have more control over your routing.

02:47 And that's where you can also have these route tables at the subnet level.

02:52 Again we are going to see examples of that.

02:55 But Essentially, route table defines the routing configuration for your VPC and your subnet.

03:02 So as of now we are talking about the VPC which is like a private address space for you.

03:08 Now imagine you are sitting at home and you launched an EC2 instance in this VPC.

03:12 Can you reach to that instance so far?

03:15 No, because this VPC is not connected to the internet.

03:19 So another important thing for VPC is the internet gateway which connects your VPC to the internet.

03:27 So that is called internet gateway.

03:30 And it enables that connectivity to the internet.

03:33 So we are going to also talk about the role of internet gateway and how to configure routing in the

03:39 subnet to allow this traffic to flow to this EC2 instance from the internet.

03:46 Right.

03:46 So this is all about the routing or network configurations.

03:51 So now let's also talk about the security of the network.

03:56 So for the VPC.

03:58 AWS provides two basic firewalls, that is security group and network ACL.

04:05 So security Group works at the EC2 instance level, which means any traffic that goes in or out of the

04:11 EC2, it can be controlled using the security group rules.

04:16 So Security Groups works at the EC2 instance level.

04:20 And the other firewall that is network access control list works at the subnet level, which means the

04:28 rules in the network ACL will be applied for all the resources which you launch inside this subnets.

04:36 And there are few other differences that you need to know between the security groups and network ACL.

04:41 And we are going to cover that in detail in the following lectures.

04:45 But at high level, these are the two basic firewalls that you can have inside your VPC.

04:52 So I hope that is clear.

04:53 Now, one more thing, which I will categorize as a part of the core component of the VPC, which is

05:00 the DNS.

05:01 How does this EC2 machine resolve the DNS as it reaches outside this VPC or within the VPC?

05:09 So you know that DNS is the most important part because it resolves the domain name to the IP addresses.

05:15 So how AWS resolves the DNS queries from this EC2 machines.

05:20 And that is done using something called AWS DNS server or also called as route 53 resolver.

05:28 Now, though, it's a core and basic components of the VPC, we are going to have a separate section

05:34 covering the AWS DNS server because it's very important for your exam.

05:41 So that's about the building blocks of the VPC.

05:44 I hope this is clear.

05:45 And now we are going to dive deep into individual components.

05:49 So let's look at those now.

05:51 Thank you.