Understand and Troubleshoot Partial DNS Failures
DNS is a large distributed hierarchical database, meaning that each domain is required to have a set of authoritative name servers answering questions about resource records for the domain. This set of authoritative name servers is under the control of the domain owner, though most domain owners delegate to a proxy to provide DNS service.
When a client needs to resolve the IP address of a domain name, the client machine hands off this process to a resolver, which finds the IP address and return it to the client. This process works as follows:
- The resolver, which is preconfigured with a list of root name servers, randomly selects one of these root name servers and asks it for a list of authoritative name servers for the top-level domain (TLD).
- The root name server responds with a list of authoritative name servers for the TLD, as well as their IP addresses.
- The resolver randomly selects one of the name servers returned in step 2 and asks it for a list of authoritative name servers for the domain.
- The TLD server responds with a list of name servers that are authoritative for the domain.
- The resolver randomly selects one, and requests the IP address of the resource record from that authoritative name server.
DNS providers serve from multiple geographies, and usually rely on cached results to improve availability; this can help to avoid temporary issues with DNS resolvers, but might also prolong recovery if bad results are cached (for example, due to negative caching). We ensure external DNS issues don't affect DNS resolution of AWS domain names within an EC2 region.
A typical DNS failure is when one or more authoritative name servers stop responding. Consider a hypothetical domain with the following list of authoritative name servers (also known as a delegation set):
- ns-576.awsdns-08.net.
- ns-1086.awsdns-07.org.
- ns-1630.awsdns-11.co.uk.
- ns-47.awsdns-05.com.
- pdns1.ultradns.net.
- pdns6.ultradns.co.uk.
If a name server is unavailable, it can’t respond to a DNS query that is directed to it; if the client doesn’t receive an answer, it can try the request with a different authoritative name server. If authoritative name servers do not respond or respond with unexpected information, the local resolver returns a SERVFAIL message.
To troubleshoot DNS failures using Linux-type operating systems, use the dig command. dig performs a lookup against the client DNS server that is configured in the /etc/resolv.conf file of your host.
相關推薦
Understand and Troubleshoot Partial DNS Failures
DNS is a large distributed hierarchical database, meaning that each domain is required to have a set of authoritative name servers answering qu
[Bash] Understand and Use Functions in Bash
n this lesson, we'll go over how bash functions work. Bash functions work like mini bash scripts--you can pass parameters and invoke them just like
DNS and BIND
dns and bindDNS and BindBIND:Berkeley internet name Domain, 伯克利互聯網名稱域;名稱域--名字空間: 倒置的樹 根域(.) 頂級域(Top Level Domain, TLD) 組織域: com, org, edu,
Communication error.Please check your DNS settings and use diagnostic
往常慣例，Upload API包，結果就報錯了：Could not find version:latest of iTMSTransporter to download，還有什麼DNS的問題 猛一看，DNS，這是網路的問題啊。 但是咱也得先嚐試一下能不能解決啊，不能順手就把鍋甩出去了，畢
Best (and Free!!) Resources to Understand Nuts and Bolts of Deep Learning
The internet is filled with tutorials to get started with Deep Learning. You can choose to get started with the superb Stanford courses CS221&nbs
Effective Five Directional Partial Derivatives-Based Image Smoothing and a Parallel Structure Design
Abstract 影象平滑已被用於影象分割，影象重建，物件分類和3D內容生成。 在預處理步驟中使用了幾種平滑方法來保持關鍵邊緣，同時去除噪聲和小細節。 為了提供快速和準確的平滑，我們提出了一種有效的方案，該方案使用平滑影象的梯度，拉普拉斯運算元和對角線導數的加權組合。 對於計算
A Gentle Introduction to Autocorrelation and Partial Autocorrelation (譯文)
A Gentle Introduction to Autocorrelation and Partial Autocorrelation 原文作者：Jason Brownlee 原文地址：https://machinelearningmastery.com/gentle-introdu
How to cover artificial intelligence and understand its impact on journalism: MOOC in Spanish, in partnership with Microsoft
The term "artificial intelligence" has been around since 1956, and yet many journalists are unfamiliar with its history and impact on the world today, even
Ask HN: Please help me understand why the SEC settled with Elon Musk and Tesla
I don't want to talk about Elon Musk or Tesla here (it's valid conversation topic, but there's been a lot said already). I strictly want to understand why
Ask HN: What are good projects to understand CUDA and GPU Programming?
I have taken an Introduction to GPU Programming Course in my college and I want to do a project which covers all the details that I have learned. Something
A Visual Way to Understand the Pros and Cons of a Decentralized Exchange
TL;DR: This is a short and no way comprehensive analysis on the pros and cons of centralized versus decentralized cryptocurrency exchanges. By the end you
3 Models to Understand, Predict, and React to Your Social Media
Want to know how to predict and forecast your followers' behavior? Wonder what modeling techniques can help you predict the lifetime value of your customer
Understand Android Activity's launchMode: standard, singleTop, singleTask and singleInstance
Activity is one of the most brilliant concept on Android from its well-design architecture on memory management which lets Multitasking w
Computer Networks and how to actually understand them
Class A: As shown in the third column of the above image, for Class A IP addresses, the first bit of the first octet of IP address is constant and is “0”.T
Creating visualizations to better understand your data and models (Part 1)
The Cancer Genome Atlas Breast Cancer DatasetThe Cancer Genome Atlas (TCGA) breast cancer RNA-Seq dataset (I’m using an old freeze from 2015) has 20,532 fe
AI and why we over-trust what we don't understand | AITopics
Are you a concerned citizen of the modern world? Do you ever worry that algorithms are stealing your data? Do you secretly have little idea what algorithms
Understand How IAM and Organizations Interact
AWS Organizations does not replace associating IAM policies with users, groups, and roles within an AWS account. IAM policies let yo
A Gentle Introduction to Autocorrelation and Partial Autocorrelation
Tweet Share Share Google Plus Autocorrelation and partial autocorrelation plots are heavily used
Understand Multivalue and Simple Routing Policies
When a client makes a DNS request, Route 53 returns all three listed IP addresses. Note: You can't attach a health check to a simple
Troubleshoot Access Issues for Websites that Use Route 53 DNS Services
Check the website's public hosted zone resource records sets Important: At a minimum, the public hosted zone must contai