网络课程笔记

00:00 Hello and welcome to this section, AWS Transit Gateway.

00:03 Now, Transit Gateway is one of the top three sections which are important for your AWS

00:09 networking certification.

00:11 Other two being AWS Direct Connect and AWS Site to Site VPN.

00:15 Now, having said that, it doesn't mean that other sections are not important, but most

00:20 of the questions in your exam will be from these three sections.

00:23 So Transit Gateway is very important and make sure that you understand everything that we

00:28 discuss in this section.

00:30 And one more thing that I want to mention at this point is that it is difficult to just

00:35 understand the Transit Gateway and all its features without understanding the Direct

00:41 Connect and the Site to Site VPN, because in reality, all these three components typically

00:47 work together to build some architecture.

00:51 So in this section, I have tried my best to keep the discussion focused on the Transit

00:56 Gateways, but ultimately, you will be able to connect all these dots after you complete

01:01 your other section and specifically the VPN and the Direct Connect section.

01:08 So bear with me for this section.

01:10 If you think that we haven't covered the VPN or DX to the right depth in this section,

01:16 we are going to cover that in the following sections.

01:20 So I hope that is understood.

01:22 Okay, so what is Transit Gateway?

01:25 Now, I hope you already know at this point what is Transit Gateway and why they were introduced.

01:29 But just to give you a brief history, Transit Gateways were introduced in 2018 and intent

01:34 was to simplify the AWS networking when it comes to managing the multiple VPCs and when

01:41 you have to have the hybrid connectivity between AWS and on-premises network.

01:47 So one of the key benefits of using Transit Gateway is to simplify the inter-VPC network.

01:47 And let me show you that with a simple example.

01:56 So assuming you have multiple VPCs and you want to have inter-VPC communication.

02:01 Now without Transit Gateway, you know that you would have to do VPC peering connection

02:06 and VPC peering connection is one-to-one, which means you have to attach two VPCs to

02:11 each other and VPC peering doesn't provide the transitive routing, which means if VPC

02:17 to B and B is connected to C, then A cannot communicate with the VPC C.

02:23 So in order to enable the communication between VPC A and C, you have to have the VPC peering

02:28 connection set up between VPC A and C.

02:32 Now that complicates this architecture a lot.

02:35 Now imagine that all these six VPCs need to communicate with each other.

02:40 Then how many peering connections you would need?

02:42 So the answer isn't simple.

02:44 If you see this, there are 15 VPC peering connection that you will need.

02:50 The point here is that you can't manage the network like this, right?

02:54 It was very difficult and that's where AWS introduced Transit Gateway, which greatly

02:59 simplifies this architecture to as simple as this.

03:03 So you connect all your VPCs to the Transit Gateway and then Transit Gateway can enable

03:08 the inter-VPC communication.

03:11 Now in this entire section, we are going to cover a lot about the Transit Gateway.

03:16 So first thing, it allows the communication between VPCs as well as between AWS and the

03:23 hybrid on-premises network.

03:25 Now Transit Gateway supports different kinds of attachments.

03:29 So we just saw the VPC attachment, but Transit Gateway also supports peering connection between

03:35 the Transit Gateways.

03:36 Now this is because Transit Gateways are regional routers.

03:40 That means you can only attach the VPCs in the same region as Transit Gateways.

03:45 Now if you want to enable the communication between VPCs across different regions, then

03:50 rather you can create Transit Gateway in the respective regions and then you can peer the

03:54 Transit Gateway in the same way you peer the VPCs across different regions.

04:00 And again, we are going to dive deep into this architecture.

04:03 So that's the second kind of attachment.

04:05 There is a third attachment type, which is extending your SD-WAN network and connect

04:10 it to AWS network using the Transit Gateway.

04:13 Again, we are going to see that.

04:16 And with respect to the hybrid connectivity, there is a VPN attachment and there is a Direct

04:21 Connect Gateway attachment, which allows Transit Gateway to connect to the Direct Connect connection.

04:27 Further, there is now a new type of attachment that Transit Gateway supports and that is

04:32 called Network Function attachment.

04:34 And it is used to connect the AWS Network Firewall directly to the Transit Gateway.

04:40 And this greatly simplifies how can you centralize the traffic inspection using the Transit Gateway.

04:46 And this is a relatively new feature, which was launched during the re-invent 2025.

04:51 And hence, we are going to dive deeper into this when we talk about AWS Network Firewall.

04:56 Because same type of the network functions you can use across different AWS networking services.

05:02 For example, as you can see, you can use it with Transit Gateway, otherwise, you can also

05:06 use the same directly with the VPC or you can use this network functions with AWS Cloud WAN service.

05:12 So, we are going to talk about this network functions across different topics.

05:17 And hence, in this section, we will only talk about this in the context of Transit Gateway.

05:22 Alright, so these are the different attachment types that Transit Gateway supports.

05:27 And apart from that, there are many features of the Transit Gateway that you should know.

05:32 And these features are like multicast support, the maximum transmission unit, then appliance

05:36 mode, easy consideration, and sharing the Transit Gateway across different AWS account.

05:43 So, for your exam, you should know all these features.

05:47 Now, lastly, because Transit Gateway has so many features and so many attachment types,

05:47 there are different architectures that you can build using the Transit Gateway.

05:57 And that's where in this section, we are going to spend a good amount of time understanding

06:02 different architectures.

06:04 And if you see, all these architectures will typically have a theme of centralizing the network.

06:10 For example, how can you centralize the traffic inspection?

06:15 How can you centralize the egress traffic that goes from all your spoke VPCs to the internet?

06:21 Or how can you centralize the VPC endpoints using the Transit Gateways?

06:26 And these are just a few.

06:27 You can simply just go on building these different kind of amazing architectures using Transit Gateway.

06:34 And these are also important for your exam.

06:36 So, in the rest of the section, we are going to talk about this attachment, this Transit

06:40 Gateway features, and more importantly, the Transit Gateway architecture.

06:45 Alright, so I hope it is clear.

06:48 And with that, now let's get started.