Lecture 201: Routing Policy - Simple
- 课程：[NEW] AWS Certified Advanced Networking Specialty 2026
- 视频时长：04:05
- 来源：Udemy Lecture 28556397
- Slide 数量：5
- 画面切换：00:55、02:03、02:44、03:23
扫描说明
逐条读取了 Udemy 页面中的 103 条英文 Transcript cue，并按时间轴扫描全长约 04:05 的视频。依据 Routing Policy 定义、Simple 多 Value 行为、创建单 Value Record、加入第二个 IP、dig 与 Browser 验证划分为 5 个小节。截图均在 Transcript 侧栏关闭、播放器控件隐藏后复核，统一为 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. Routing Policy 只决定 DNS Answer，不转发业务流量
时间范围：00:00–00:55
总结 / Summary
中文
Route 53 的 Routing Policy 决定 DNS Query 应返回什么 Answer，不像 Load Balancer 那样真正转发业务 Traffic。DNS 只把 Hostname 翻译成客户端可使用的 Endpoint；随后 HTTP 等连接由 Client 直接发往该 Endpoint。Route 53 支持 Simple、Weighted、Failover、Latency、Geolocation、Multi-value Answer 与 Geoproximity 等策略。
English
A Route 53 routing policy determines which answer a DNS query receives; it does not forward application traffic like a load balancer. DNS only translates a hostname into an endpoint the client can use, after which the client connects directly. Route 53 supports Simple, Weighted, Failover, Latency, Geolocation, Multi-value Answer, and Geoproximity policies.
Transcript
00:00 So now let's talk about routing policies
00:01 for Route 53.
00:03 So a routing policy is helping Route 53
00:05 respond to DNS queries,
00:07 and we shouldn't be confused about the word routing.
00:11 This is not like when you have a load balancer and the
00:13 actual load balancer will route traffic
00:15 to the backend EC2 instances.
00:17 No, no, no.
00:18 This routing is from a DNS perspective.
00:21 So the DNS does not respond, does not route any traffic.
00:24 So the traffic doesn't go through the DNS.
00:26 The DNS only will respond to the DNS queries
00:28 and then the clients will know to which way
00:31 they should be doing these HTTP queries, for example.
00:35 So the DNS just helps translate host names
00:37 into actual endpoints that the clients can use.
00:40 So Route 53 will support the following routing policy.
00:44 There's simple, weighted, failover, latency based,
00:47 geolocation, multi-value answer, and geoproximity.
00:51 And we're going to have a look at all of them
00:53 in this section.
2. Simple 可返回一个或多个 Value，由 Client 随机选择
时间范围：00:55–02:03
总结 / Summary
中文
Simple Routing 通常把名称指向一个 Resource，但同一 Record 也可配置多个 Value。Route 53 会把全部 Value 一起返回，随后由 Client 在本地随机选择一个，因此它不是由 Route 53 执行的均衡算法。Simple Alias 只能指定一个 AWS Resource Target，而且 Simple Policy 不能直接关联 Health Check。
English
Simple routing usually points a name to one resource, but a single record may contain multiple values. Route 53 returns all values and the client randomly selects one locally, so Route 53 itself is not performing load balancing. A simple alias can target only one AWS resource, and the simple policy cannot be associated directly with a health check.
Transcript
00:55 So the first one is going to be the simple routing policy.
00:58 And the idea is that with this,
01:00 that we've actually been using before,
01:02 we're going to route traffic to a single resource typically.
01:05 So here's an example.
01:06 The clients that will say, hey,
01:07 I want to go to foo.example.com,
01:09 and Routes 53 will say, hey,
01:11 go to this IP address.
01:13 And this is an A record.
01:14 So it is possible for us to specify multiple values
01:17 in the same record.
01:19 And if so, if multiple values are returned by the DNS,
01:22 then a random one will be chosen by the clients
01:25 or client side.
01:26 So in this example,
01:27 we have the client's asking again for foo.example.com,
01:30 and Amazon Route 53 will just reply with three IP addresses
01:34 that occur embedded into the A record.
01:37 And then the clients will pick one of them randomly
01:40 and apply it for the routing.
01:42 So if you have enabled an alias record alongside
01:45 the simple policy,
01:47 then you can only specify on AWS resource as a target.
01:51 And finally, it's called simple because it's very simple.
01:52 And therefore you can not associate this with health checks
01:55 and we'll see health checks later on in this section
01:57 and how they work.
01:57 So let's go in the console to see how a routing policy
02:00 of step simple can be created.
3. 创建 TTL 20 秒的 Simple A Record 指向 Singapore
时间范围：02:03–02:44
总结 / Summary
中文
在 Hosted Zone 中创建 simple.stephanetheteacher.com，Type 选 A，Value 填 ap-southeast-1 EC2 的 Public IP，TTL 设为 20 秒，Routing Policy 选 Simple。记录生效后，浏览器访问该名称返回 ap-southeast-1b 的 Hello World，证明单 Value 的 Simple Record 正常解析。
English
In the hosted zone, create simple.stephanetheteacher.com as an A record whose value is the public IP of the ap-southeast-1 EC2 instance. Set TTL to 20 seconds and choose Simple routing. Once active, browsing to the name returns the Hello World page from ap-southeast-1b, confirming single-value resolution.
Transcript
02:03 So let's create a record, and the record name is going to be
02:05 simple.stephanetheteacher.com.
02:08 It's an A record, and the value of which is going to be,
02:11 for example, my instance in ap-southeast-1.
02:15 Now for TTL, it will say something very low,
02:16 like 20 seconds.
02:17 And the routing policy is going to be here.
02:19 So as you can see, we have different possibilities,
02:22 six of them, and then one other that is
02:24 somewhere else in the UI.
02:26 So we have a TTL 20 seconds as simple writing policy,
02:29 and let's just create this record.
02:31 So we've been doing this before.
02:33 We know how this works.
02:34 So now if we go to simple.stephanetheteacher.com.
02:39 And go to this URL, we get
02:40 Hello World from my instance in ap-southeast-1b,
02:43 which is awesome.
4. 在同一 Record 中加入 Singapore 与 N. Virginia 两个 IP
时间范围：02:44–03:23
总结 / Summary
中文
先用 dig 验证 A Record 返回 Singapore IP 且 TTL 为 20 秒；然后编辑同一 Record，在 Value 中分别加入 ap-southeast-1 与 us-east-1 的两个 IP。这里不是创建两条带权重或健康检查的记录，而是在一个 Simple Record 中保存多个 Answer。
English
First, dig confirms that the A record returns the Singapore IP with a 20-second TTL. Then edit the same record and add both the ap-southeast-1 and us-east-1 IP addresses as separate values. This is one simple record containing multiple answers, not two weighted or health-checked records.
Transcript
02:44 And if we do a dig command and have a look,
02:47 so we need to reinstall dig.
02:50 So sudo yum install bind-utils.
02:52 So this is because I restarted my machine here.
02:56 Okay, we're going to redo the dig command.
02:59 So we do the dig command on this.
03:01 As we can see, we have an A record of a TTL of 20 seconds
03:04 pointing to this IP.
03:05 But we can change this record now.
03:07 We're going to edit the record.
03:10 So I will just simply click on it and edit the record.
03:12 And for the value, now, I can enter multiple IPs.
03:15 So I can insert my one in ap-southeast-1
03:17 or one in us-east-1, for example.
03:20 So when I do so and save this,
5. dig 返回两个 Answer，Browser 由客户端侧选择 Region
时间范围：03:23–04:05
总结 / Summary
中文
旧 TTL 到期后，dig 的 Answer Section 同时显示 Singapore 与 N. Virginia 两个 IP。浏览器刷新时由 Client 从返回集合中选择，所以第一次仍可能命中 ap-southeast-1b，之后也可能命中 us-east-1a。Simple Multi-value 没有健康感知与精确流量控制，不能替代 Weighted 或 Multi-value Answer Policy。
English
After the old TTL expires, the dig answer section contains both the Singapore and Northern Virginia IPs. The browser chooses from that returned set, so one refresh may still reach ap-southeast-1b and another may reach us-east-1a. Simple multi-value routing has no health awareness or precise traffic control and does not replace Weighted or Multi-value Answer routing.
Transcript
03:23 what's going to happen is that once the TTL expires
03:26 from before, we're going to get two records back.
03:28 So let's use CloudShell to verify this.
03:31 So I'm going to do a dig command.
03:33 And as you can see,
03:34 now we have in the intersection, we have two responses.
03:37 We have one in this IP and one in this IP.
03:40 So it's a client side choice.
03:42 So that means that if I go to this website and refresh,
03:44 I have one chance out of two to go into us-east-1.
03:46 And I didn't.
03:48 So I was back into ap-southeast-1b,
03:50 but let me pause for 20 seconds and I'll get back to you.
03:53 And I'm refreshing.
03:55 And I get back the Hello World from us-east-1a.
03:58 So this worked.
03:59 This absolutely shows how simple records work.
04:03 I hope you liked it, and I will see you in the next lecture.
整讲总结 / Overall Summary
中文
Route 53 Routing Policy 决定 DNS 回答，而不承载或转发流量。Simple Routing 可让一个名称返回单个或多个 Value；多个 Value 会全部交给客户端并由客户端随机选择，无法关联 Health Check，因此只适合简单映射。
English
A Route 53 routing policy determines DNS answers rather than carrying or forwarding traffic. Simple routing can return one or multiple values for a name; all multiple values are given to the client for local random selection, and no health check can be associated, making it suitable only for straightforward mappings.
返回顶部 ↑