Lecture 142: DX support for MTU and Jumbo Frames
- 课程：[NEW] AWS Certified Advanced Networking Specialty 2026
- 视频时长：04:00
- 来源：Udemy Lecture 27898874
- Slide 数量：12
- 画面切换：00:48、00:57、01:05、01:23、01:43、01:53、02:05、02:17、02:39、03:05、03:32
扫描说明
逐条检查了 Udemy 页面中的 85 条 Transcript cue，并扫描了全长约 4:00 的视频。根据标题页、MTU 历史说明、连接启用状态、各类 VIF 的 MTU 限制、完整拓扑、路由传播规则和路由表示例的逐项渐显，共划分为 12 个小节。最终截图均在精确 Transcript cue 暂停后关闭侧栏、移出指针并截取完整视频媒体区域；12 张图片没有黑边、顶部课程栏、底部或中心播放器控件，也没有右侧或下方裁切，并统一输出为 1364×770。
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. Direct Connect MTU 与 Jumbo Frames 概览
时间范围：00:00–00:48
总结 / Summary
中文
最大传输单元（Maximum Transmission Unit，MTU）表示网络能够传输的最大数据包字节数。巨型帧（Jumbo Frames）通过减少传输同等数据所需的数据包数量，提高网络吞吐量（Throughput）。
English
The Maximum Transmission Unit (MTU) is the largest packet size, in bytes, that a network can carry. Jumbo Frames improve throughput by reducing the number of packets required to transfer the same amount of data.
Transcript
00:00 Hello, and welcome to this lecture.
00:02 Now if you remember,
00:03 our lecture about the network performance,
00:06 in that lecture, we talked about the MTU and Jumbo Frames.
00:10 And if you remember, we said that
00:12 Jumbo Frames allows the larger packet size
00:15 to flow over the network,
00:16 which ultimately improves
00:18 the network performance and the throughput
00:20 because less number of packets
00:22 are required to transmit the data.
00:24 And then we also saw when it comes to the VPC,
00:28 what is an MTU that is supported
00:30 when the traffic flows over to the internet
00:32 or between VPCs over a VPC peering connection
00:35 or through a VPN connection, right.
00:39 Now, let's see how it is structured
00:42 when it comes to the Direct Connect connection.
00:46 So just a quick recap,
2. MTU 定义与基础拓扑
时间范围：00:48–00:57
总结 / Summary
中文
在 Direct Connect（DX）链路中，MTU 是可通过连接传递的最大数据包大小；配置必须从 AWS 侧连接一直兼容到客户路由器（Customer Router）。
English
On a Direct Connect link, MTU is the largest packet that can cross the connection. The configuration must be compatible from the AWS side through to the customer router.
Transcript
00:48 MTU is the size in bytes of the largest permissible packet
00:53 that can be passed over the network.
00:55 Now with respect to the DX connection,
3. 2018 年以前仅支持 1500 MTU
时间范围：00:57–01:05
总结 / Summary
中文
截至 2018 年 10 月之前，Direct Connect（DX）仅支持 1500 字节 MTU，因此不能在 DX 连接上使用巨型帧（Jumbo Frames）。
English
Until October 2018, Direct Connect supported only a 1,500-byte MTU, so Jumbo Frames were unavailable on DX connections.
Transcript
00:57 until 2018 DX did not support the Jumbo Frames.
01:02 That means MTU was 1500.
4. DX 现已支持 9001 MTU
时间范围：01:05–01:23
总结 / Summary
中文
Direct Connect（DX）后来开始支持最高 9001 字节 MTU，即巨型帧（Jumbo Frames）；但必须在底层 DX 连接上显式启用。
English
Direct Connect later added support for MTUs up to 9,001 bytes—Jumbo Frames—but the feature must be explicitly enabled on the underlying DX connection.
Transcript
01:05 But post 2018, AWS started supporting
01:09 the Jumbo Frames for DX connections.
01:13 So as of today, you can obviously use Jumbo Frames
01:16 on the Direct Connect connections,
01:18 but for that, you have to enable that
01:20 on the Direct Connect connection.
5. 底层连接必须启用 Jumbo Frames
时间范围：01:23–01:43
总结 / Summary
中文
在虚拟接口（Virtual Interface，VIF）上使用巨型帧（Jumbo Frames）前，底层 Direct Connect 连接或链路聚合组（Link Aggregation Group，LAG）也必须具备并启用巨型帧能力。
English
Before a Virtual Interface can use Jumbo Frames, the underlying Direct Connect connection or Link Aggregation Group must also be Jumbo-Frame capable and enabled.
Transcript
01:23 Now, this does not mean that you can use Jumbo Frames,
01:26 irrespective of the type of the virtual interfaces
01:29 you are creating on top of Direct Connect connection.
01:32 And shortly, we'll see whether you can use Jumbo Frames
01:35 with respect to the Private VIF or a Public VIF
01:39 or a Transit VIF.
01:41 So very first thing to remember,
6. Public VIF 不支持 Jumbo Frames
时间范围：01:43–01:53
总结 / Summary
中文
公共虚拟接口（Public VIF）不支持巨型帧（Jumbo Frames），只能使用标准 1500 字节 MTU。
English
A Public VIF does not support Jumbo Frames and uses the standard 1,500-byte MTU.
Transcript
01:43 public VIFs don't support Jumbo Frames,
01:47 and when it comes to the Transit VIF or Private a VIF,
7. Transit VIF 支持 1500 或 8500 MTU
时间范围：01:53–02:05
总结 / Summary
中文
中转虚拟接口（Transit VIF）支持 1500 或 8500 字节 MTU；8500 字节模式属于巨型帧（Jumbo Frames）。
English
A Transit VIF supports an MTU of either 1,500 or 8,500 bytes; the 8,500-byte mode is a Jumbo Frame configuration.
Transcript
01:53 Transit VIF support the MTU of 1500 or 8500.
01:59 So Transit VIF also supports, you can say Jumbo Frames,
02:02 but the size is 8500.
8. Private VIF 支持 9001 MTU
时间范围：02:05–02:17
总结 / Summary
中文
私有虚拟接口（Private VIF）支持 9001 字节 MTU，适用于连接虚拟私有网关（Virtual Private Gateway，VGW）或 Direct Connect Gateway 的场景。
English
A Private VIF supports a 9,001-byte MTU when attached through a Virtual Private Gateway or Direct Connect Gateway.
Transcript
02:05 However, Private VIFs support the MTU of 9001
02:09 which is again, a Jumbo Frame.
02:11 Now this is supported when Private VIF
02:13 is attached to the Virtual Private gateway
02:15 or Direct Connect gateway.
9. VIF 与底层 DX/LAG 能力必须匹配
时间范围：02:17–02:39
总结 / Summary
中文
即使虚拟接口（VIF）本身支持较大 MTU，底层 Direct Connect 连接或链路聚合组（LAG）若未启用巨型帧（Jumbo Frames），VIF 的巨型帧配置也不会生效。
English
Even if a VIF supports a larger MTU, its Jumbo Frame setting is ineffective unless the underlying Direct Connect connection or LAG is Jumbo-Frame capable and enabled.
Transcript
02:17 And this is required that
02:20 when you have to use Jumbo Frames on the VIFs
02:23 of course the underlying Direct Connect connection
02:26 or LAG should also be supporting the Jumbo Frames.
02:30 So there is no point
02:31 if the connection is not enabled for Jumbo Frames,
02:34 then creating a VIFs with Jumbo Frames enabled
02:37 doesn't help right?
10. 三类 VIF 的 MTU 对照
时间范围：02:39–03:05
总结 / Summary
中文
在同一条启用巨型帧（Jumbo Frames）的 DX 连接上，公共虚拟接口（Public VIF）仍为 1500 MTU，私有虚拟接口（Private VIF）可达 9001 MTU，中转虚拟接口（Transit VIF）可达 8500 MTU。
English
On the same Jumbo-Frame-enabled DX connection, a Public VIF remains at 1,500 MTU, a Private VIF can use 9,001 MTU, and a Transit VIF can use 8,500 MTU.
Transcript
02:39 So this is how it looks like,
02:41 you have the connection, which is Jumbo Frame enabled.
02:44 And on top of that connection,
02:46 you can have Public VIF or a Private VIF or a Transit VIF.
02:49 Public VIF do not support Jumbo Frames,
02:52 but Private VIF does and so as the Transit VIF.
02:57 So just remember this and this should be sufficient
03:00 for your exam.
03:01 Just one more, last thing about the Jumbo Frames.
11. 仅传播路由使用 Jumbo Frames
时间范围：03:05–03:32
总结 / Summary
中文
Direct Connect（DX）的巨型帧（Jumbo Frames）只应用于传播路由（Propagated Routes）；通过静态路由（Static Routes）发送的流量仍使用默认 1500 MTU。
English
Direct Connect Jumbo Frames apply only to propagated routes. Traffic sent through static routes continues to use the default 1,500-byte MTU.
Transcript
03:05 Jumbo Frames are applied
03:07 only to the propagated routes for the DX.
03:11 And if there is a static route,
03:12 then the default 1500 MTU is used.
03:16 And this is something again,
03:18 I don't think so, really you need to remember all this,
03:21 just remember that DX now support the Jumbo Frames
03:24 and Public VIF do not support jumbo frames,
03:27 where as Transit VIF and Private VIF support Jumbo Frames.
12. 路由表示例：Static 与 Propagated
时间范围：03:32–04:00
总结 / Summary
中文
VPC 路由表（VPC Route Table）可同时包含本地或静态路由（Static Routes）以及由虚拟私有网关（VGW）传播的路由（Propagated Routes）；只有后者能够沿 DX 私有虚拟接口使用巨型帧（Jumbo Frames）。
English
A VPC route table can contain local or static routes alongside routes propagated by a Virtual Private Gateway. Only the propagated routes can use Jumbo Frames across the DX Private VIF.
Transcript
03:32 So about this route table,
03:34 if you have a route table in your VPC,
03:36 and there is a propagated route through
03:38 Virtual Private gateway through the, you know, Private VIF
03:42 then Jumbo Frames are supported
03:43 only on the propagated route, not the static route.
03:46 So just remember that.
03:48 So that's it for this lecture
03:49 where we quickly understood about the Jumbo Frames
03:53 over the DX.
03:54 And with that, we will just move to the next lecture.
03:58 So thanks for watching.
整讲总结 / Overall Summary
中文
Direct Connect（DX）现已支持巨型帧（Jumbo Frames），但 MTU 上限取决于虚拟接口（VIF）类型：公共虚拟接口（Public VIF）为 1500，私有虚拟接口（Private VIF）为 9001，中转虚拟接口（Transit VIF）为 8500。使用较大 MTU 时，底层 DX 连接或链路聚合组（LAG）必须先启用巨型帧。此外，巨型帧只适用于传播路由（Propagated Routes），静态路由（Static Routes）仍按 1500 MTU 发送。
English
Direct Connect now supports Jumbo Frames, but the MTU ceiling depends on the VIF type: 1,500 for a Public VIF, 9,001 for a Private VIF, and 8,500 for a Transit VIF. The underlying DX connection or LAG must be Jumbo-Frame enabled before a VIF can use the larger MTU. Jumbo Frames apply only to propagated routes; static routes continue to send traffic with a 1,500-byte MTU.
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