Lecture 117: BGP Autonomous System (AS) and ASN
- 课程：[NEW] AWS Certified Advanced Networking Specialty 2026
- 视频时长：05:37
- 来源：Udemy Lecture 39622856
- Slide 数量：14
- 画面切换：00:12、01:28、02:14、02:25、02:29、02:57、03:31、03:46、03:55、04:18、04:28、04:32、04:40
扫描说明
逐条检查了 Udemy 页面中的 104 条 Transcript cue，并以每条 cue 对应画面扫描了全长约 5:37 的视频。依据标题、BGP 对等体示意图的两种状态，以及 ASN 幻灯片逐项揭示的十一种状态，共划分为 14 个小节。正式截图均在视频播放且控件隐藏后，按真实媒体边界截取为 1364×770，并逐张复核。
Transcript 来自 Udemy 页面自带的英文自动字幕，没有使用 ASR。下面保留页面原文，包括其中的语法或识别错误。
1. BGP AS 与 ASN 导入
时间范围：00:00–00:12
总结 / Summary
中文
本讲介绍建立 Direct Connect（DX）边界网关协议（Border Gateway Protocol, BGP）会话所需的自治系统（Autonomous System, AS）与自治系统号（Autonomous System Number, ASN）概念。
English
This lecture introduces Autonomous Systems and Autonomous System Numbers, which are required when establishing BGP sessions over AWS Direct Connect.
Transcript
00:00 Hi,
00:00 let's quickly understand about the BGP
00:03 autonomous system and autonomous system number.
00:06 Again, important for setting up the BGP session
00:10 on the DX network.
2. Direct Connect 中的 BGP 端点
时间范围：00:12–01:28
总结 / Summary
中文
Direct Connect 连接可承载公有虚拟接口（public VIF）、私有虚拟接口（private VIF）和传输虚拟接口（transit VIF）。这些 VIF 在 AWS 一侧分别连接 AWS 托管路由器、虚拟私有网关（Virtual Private Gateway, VGW）、Direct Connect 网关（Direct Connect Gateway, DXGW）或传输网关（Transit Gateway, TGW），共同构成路由端点。
English
A Direct Connect connection can carry public, private, and transit VIFs. On the AWS side they terminate on an AWS-managed router, VGW, DXGW, or TGW, depending on the VIF type.
Transcript
00:12 So
00:12 you know this
00:13 diagram,
00:14 if not, we are going to cover this in more detail. But
00:17 once you have the DX connection on that connection,
00:21 you can create a public VIF which connects you to the public AWS services
00:26 or there could be a private VIF which is shown in the red.
00:30 Now,
00:30 private VIF can be connected to DirectConnect Gateway or it can directly be
00:35 connected to the virtual private Gateway which is attached to the VPC.
00:39 And there is third type of the VIF which is Transit VIF and Transit VIF
00:44 first connects to DX Gateway and then it can be attached to the Transit Gateway,
00:50 which means on AWS side, these VIFs connect to different networking component.
00:56 Now, in case of public VIF, it is AWS managed router which you don't see.
01:02 But in case of private VIF and a Transit VIF,
01:06 these are the components which you configure.
01:09 So whether it's DX Gateway or it is a virtual private Gateway.
01:14 Now,
01:14 all these are the Routing component on AWS side
01:18 and they represent the AWS side of the network,
01:21 which is called autonomous system.
01:24 So in the BGP world, these are called the BGP peers.
3. BGP Peers 与 AS
时间范围：01:28–02:14
总结 / Summary
中文
BGP 会话连接两个对等体（BGP peers）：一端是客户网络中的路由器，另一端是所选 VIF 对应的 AWS 路由组件。每一侧代表一个自治系统（Autonomous System, AS），其自治系统号（ASN）要在创建 VIF 或配置 BGP 会话时提供。
English
A BGP session connects two peers: the customer router and the AWS routing component selected by the VIF design. Each side represents an AS whose ASN is supplied during VIF creation or BGP configuration.
Transcript
01:28 So one end will be your router on your network
01:32 and other end will be AWS side of the routers.
01:35 And depending on what kind of VIF you create, this peers will differ.
01:39 Now, in this case, it is a Peering connection
01:42 between the AWS router
01:45 and your router for the public VIF connection. Similarly,
01:49 if you are creating a private VIF and attaching it to the DX Gateway,
01:54 then it will be the AS for
01:56 BGP peer
01:57 similarly for other connections.
02:00 So all these ASs would have the numbers and those numbers you have to
02:05 provide while you create the BGP session or when you create the virtual interfaces.
02:12 So let's talk about those.
4. 客户路由器需要 ASN
时间范围：02:14–02:25
总结 / Summary
中文
企业路由器通过 Direct Connect 连接 AWS 时必须配置自治系统号（Autonomous System Number, ASN）。客户侧 ASN 可以使用公有 ASN（public ASN）或私有 ASN（private ASN），具体选择取决于路由交换场景。
English
The customer router needs an ASN when it connects to AWS through Direct Connect. The customer side may use either a public ASN or a private ASN, depending on the routing scenario.
Transcript
02:14 OK. Now let's look at the autonomous system number that is ASN.
02:18 So when you configure your side of the router
02:20 and connect it to the DirectConnect,
02:23 you have to provide the ASN numbers to your router.
5. Public 与 Private ASN
时间范围：02:25–02:29
总结 / Summary
中文
ASN 分为公有自治系统号（public ASN）与私有自治系统号（private ASN）。公有 ASN 类似公有 IP 地址或域名，需要由组织拥有并用于可公开识别的自治系统。
English
ASNs can be public or private. A public ASN is comparable to a public IP address or domain name because an organization must own it for globally identifiable routing.
Transcript
02:25 Now this ASN could be public or private.
6. IANA 与 Regional Internet Registries
时间范围：02:29–02:57
总结 / Summary
中文
公有 ASN（public ASN）由互联网号码分配机构（Internet Assigned Numbers Authority, IANA）通过区域互联网注册管理机构（Regional Internet Registries, RIRs）分配，因此客户必须拥有合法分配的号码。
English
Public ASNs are allocated by IANA through the Regional Internet Registries, so the customer must own a legitimately assigned number.
Transcript
02:29 Now, if you talk about the public ASN,
02:32 this is very similar to maybe a public Domain name or IPs which you have to own.
02:37 So public
02:39 ASN are assigned by the IANA
02:41 that is internet
02:42 assigned number authority. You can go to IANA org and check more about this.
02:47 So this has to be owned by the customer, right?
02:50 And
02:51 you need to use this public ASN if you are
02:54 exchanging the BGP routes over a public internet.
7. 公有路由交换使用 Public ASN
时间范围：02:57–03:31
总结 / Summary
中文
如果要通过公共互联网（public Internet）交换 BGP 路由，应使用公有 ASN（public ASN）。AWS Direct Connect 同时允许客户侧选择公有或私有 ASN，但两者在后续路由策略中的行为有所不同。
English
A public ASN is required when BGP routes are exchanged over the public Internet. Direct Connect supports both public and private customer ASNs, although later routing behavior differs between them.
Transcript
02:57 Now,
02:58 with respect to the AWS, you have
03:00 the option where you want to use public ASN or a private ASN and things change
03:06 a little when you use public or a private ASN that we will cover in the next lectures.
03:11 But both options are there. Now with respect to the ASN numbers
03:15 E A
03:16 has defined the range of ASN numbers for use.
03:19 And that really depends on whether you are using 16 bit ASN number
03:23 that is two byte or 32 bit ASN numbers which are four bytes
03:28 and accordingly, you can choose your ASN number.
8. Private ASN 用于私有连接
时间范围：03:31–03:46
总结 / Summary
中文
私有 ASN（private ASN）适合两个自治系统（Autonomous Systems, ASes）之间的私有连接。Direct Connect 本身是私有连接，因此客户可以在适用场景中使用私有 ASN。
English
A private ASN is suitable for private connectivity between two autonomous systems. Because Direct Connect is a private connection, it can use a private customer ASN where supported.
Transcript
03:31 As I said, you can also have the private a ASN.
03:34 So this is typically used for a private connection between two ASs.
03:39 So DirectConnect is
03:41 in that sense is a private connection. So you can very well use private
03:45 ASN,
9. 2-Byte ASN 地址空间
时间范围：03:46–03:55
总结 / Summary
中文
两字节 ASN（2-byte ASN）使用 16 位编号空间，总体范围为 0–65535。公有与私有 ASN 从这个空间中分别划定可用区间。
English
A 2-byte ASN uses a 16-bit number space ranging from 0 through 65535, with separate portions reserved for public and private use.
Transcript
03:46 OK. As I said, you could have ASN 16 bit or 32 bit.
03:51 And this is a range of ASN number defined by IANA
03:55 and
10. 2-Byte Public ASN 范围
时间范围：03:55–04:18
总结 / Summary
中文
在两字节 ASN（2-byte ASN）空间中，IANA 定义的公有 ASN（public ASN）范围为 1–64495。本讲说明的是 IANA 的通用范围，并非某个 AWS 资源单独允许的全部取值。
English
Within the 2-byte space, the general IANA public ASN range is 1–64495. This is the global range, not necessarily the exact subset accepted by every AWS resource.
Transcript
03:55 if you are using public ASN, then it should be in the range of 1 to 64495.
04:01 Now again, we are not talking here about the AWS
04:04 allowed ASN numbers for public or private ASN
04:08 but a general IANA recommended ASN numbers.
04:12 And if you are going with the private ASN
04:15 with two byte, you could assign it in the range from
11. 2-Byte Private ASN 范围
时间范围：04:18–04:28
总结 / Summary
中文
两字节私有 ASN（2-byte private ASN）的范围为 64512–65534。该空间较小，因此大型网络可能需要使用四字节 ASN（4-byte ASN）获得更多编号。
English
The 2-byte private ASN range is 64512–65534. Because this space is limited, larger networks may prefer 4-byte ASNs.
Transcript
04:18 64512 to 65535.
04:22 Now, as you know,
04:23 you might want to go for
04:24 four byte instead because this is a very limited range and in that case,
12. 4-Byte ASN 地址空间
时间范围：04:28–04:32
总结 / Summary
中文
四字节 ASN（4-byte ASN）使用 32 位编号空间，总体范围为 0–4294967295，显著扩展了可分配的自治系统号数量。
English
A 4-byte ASN uses a 32-bit number space ranging from 0 through 4294967295, greatly increasing the pool of available AS numbers.
Transcript
04:28 this range is 0 to that big number
13. 4-Byte Public ASN 范围
时间范围：04:32–04:40
总结 / Summary
中文
四字节公有 ASN（4-byte public ASN）由 IANA 分配，其通用范围为 1–2147483647。具体 AWS 组件仍可能实施更窄的允许范围。
English
The general IANA range for 4-byte public ASNs is 1–2147483647, although individual AWS components may accept a narrower subset.
Transcript
04:32 and public ASNs are in the range from 1 to
04:36 that range. And private ASN are in the range of
14. 4-Byte Private ASN 与 AWS 资源限制
时间范围：04:40–05:37
总结 / Summary
中文
四字节私有 ASN（4-byte private ASN）的范围为 4200000000–4294967294。创建虚拟接口（Virtual Interface, VIF）、Direct Connect 网关（DXGW）或传输网关（TGW）时，可用 ASN 范围会因资源类型而异，但都属于 IANA 定义的总体编号空间。
English
The 4-byte private ASN range is 4200000000–4294967294. The subset accepted by a VIF, DXGW, or TGW varies by resource type, but all values come from the broader IANA-defined number space.
Transcript
04:40 the range that is given here.
04:42 Now,
04:43 with respect to the AWS,
04:45 what kind of ASN number you can use really depends on where you are using it.
04:50 So for example, if you are creating the VIFs which are virtual interfaces,
04:55 then there is a different ASN range that you can use.
04:58 However, if you are using or creating the
05:02 components like DirectConnect Gateway or Transit Gateway, in that case,
05:07 there is a separate ASN range that you can use.
05:10 But ultimately, it will be from this overall range defined by the IANA
05:14 Ok,
05:15 So that's it about the BGP AS
05:18 and the ASN.
05:19 Now we will refer to these terms more often whenever we speak about
05:23 the virtual interfaces and different settings
05:26 while talking about the DX connections.
05:29 So I hope uh this session helps you recollect what that means.
05:34 So thanks for watching and stay tuned.
整讲总结 / Overall Summary
中文
BGP 把客户路由器与 AWS 侧路由组件视为两个对等自治系统（Autonomous Systems, ASes），双方用自治系统号（ASN）标识。客户侧可按场景使用公有 ASN（public ASN）或私有 ASN（private ASN）；IANA 为 2-byte 与 4-byte 编号空间定义公有和私有范围，而 AWS 各类 VIF、DXGW 与 TGW 还会施加各自的取值限制。
English
BGP treats the customer router and the AWS routing component as peer autonomous systems identified by ASNs. The customer can use public or private ASNs as appropriate. IANA defines public and private ranges for both 2-byte and 4-byte spaces, while AWS VIFs, DXGWs, and TGWs impose resource-specific subsets.
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