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Troubleshooting NetScaler
Troubleshooting NetScaler

Troubleshooting NetScaler: Gain essential knowledge and keep your NetScaler environment in top form

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Troubleshooting NetScaler

Chapter 2. Traffic Management Features

This chapter is focused on the features that form the basis of most NetScaler deployments. They are available under the traffic management node in the UI. These features are as follows:

  • Load balancing
  • SSL offloading
  • Content switching
  • GSLB

Let's explore and discuss troubleshooting these features one at a time.

Load balancing

The NetScaler started off as a high performance load balancer and is still its most prominent use case. In this chapter, we will look at a range of issues/questions that you come across when setting up or managing a load balanced environment with the NetScaler.

Considerations

First, let's look at some considerations around the general settings of load balancing.

Startup RR factor

Let's consider a scenario where you've created a new load balancing (LB) vServer or bound a service to an existing vServer that already has a bunch of services. You will notice that even though you have the LB method as the default (also happens to be the recommended) of least connections, NetScaler starts to send requests to the backend in a round robin fashion. This is a deliberate behavior to ensure that the new service you've just added doesn't get inundated with requests; after all, being a new server, it will have the least connections. This behavior is controlled by adjusting...

SSL

We will now look at issues that can arise when load balancing SSL applications via the NetScaler. Let's start by looking at some considerations when deploying SSL, before discussing certificates and some essential Wireshark knowledge that you need in the SSL area. We will then apply this knowledge to troubleshoot some common issues before wrapping up the section with a discussion of SSL security best practices.

SSL deployment considerations

SSL is now ubiquitous. In fact, most public facing deployments simply cannot go into production without it. Using NetScaler to take the SSL processing load off the servers is referred to as SSL offloading. SSL offloading is great for performance because a NetScaler with its specialized SSL cards is optimized for handling SSL transactions, while your application servers typically are not.

Note

While the generic name SSL has stuck, SSL is no longer the choice for security and nor is TLS 1.0. The severity of the POODLE attack that impacts both protocols...

Content switching

In this section, we will look at troubleshooting Content Switching. CS, as it is called in short, can be thought of as the single IP face of an infrastructure that is large and complex in the background. The idea is to have the CS vServer use Administrator configured rules to choose target LB vServers that each handle load balance for a particular type of content. The rules are the main value offered here as they can get very granular in identifying minute differences between two requests.

Content switching

As such, troubleshooting CS in the vast majority of cases comes down to verifying two things:

  • You have the right policies in place
  • The LB vServers that are bound are up

Troubleshooting service unavailable errors

I have a CS VIP (cs-vip) that choses either the vServer base-vip, containing only HTML, or the vServer image-vip, containing only images by looking at the URL.

Troubleshooting service unavailable errors

I try to access the VIP, and instead of the page with images that I expected to see, I land on a Service Unavailable error...

Global Server Load Balancing

Global Server Load Balancing (GLSB) does for data centers what load balancing does for servers. It directs users to the best possible resource (best data center for a resource). Best here can mean, the closest, the healthiest, or the least loaded.

GSLB uses a proprietary protocol called Metric Exchange Protocol (MEP) to obtain the metrics needed for this decision. The result of GSLB processing is an Address (A) record in response to a DNS request that the client will then use to obtain the resource.

In this section, we'll look at what a typical first time flow looks like, what some of the considerations are for GSLB to work correctly, and then move on to troubleshooting.

GSLB flow

It is important to understand the several layers involved in a GSLB conversation to be able to troubleshoot it. Let's take a look at an example of a User wanting to launch the home page of web.xmx.lab, which belongs to the xmx.lab domain:

  1. User accesses web.xmx.lab for the first...

Summary

In this chapter, we looked at how to examine and troubleshoot uneven load balancing as well as performance issues when load balancing via the NetScaler. We then extended that learning to SSL, content switching, and global server load balancing, which are all application delivery features that many large enterprises rely on to deliver their applications at scale and in a globally distributed manner.

I hope the chapter has proven useful to you. In the next chapter, we will look at how to troubleshoot caching and compression, which are RFC standards-based features that help further optimize HTTP content delivery via the NetScaler.

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Key benefits

  • Learn how the main features - Load Balancing, Content Switching, GSLB, SSL offloading, AAA, AppFirewall, and Gateway work under the hood using vividly explained flows and traces
  • Explore the NetScaler layout and the various logs, tools and methods available to help you when it’s time to debug
  • An easy-to-follow guide, which will walk you through troubleshooting common issues in your NetScaler environment

Description

NetScaler is a high performance Application Delivery Controller (ADC). Making the most of it requires knowledge that straddles the application and networking worlds. As an ADC owner you will also likely be the first person to be solicited when your business applications fail. You will need to be quick in identifying if the problem is with the application, the server, the network, or NetScaler itself. This book provides you with the vital troubleshooting knowledge needed to act fast when issues happen. It gives you a thorough understanding of the NetScaler layout, how it integrates with the network, and what issues to expect when working with the traffic management, authentication, NetScaler Gateway and application firewall features. We will also look at what information to seek out in the logs, how to use tracing, and explore utilities that exist on NetScaler to help you find the root cause of your issues.

Who is this book for?

This book is aimed at NetScaler administrators who have a basic understanding of the product but are looking for deeper exposure and guidance in identifying and fixing issues to keep their application environment performing optimally.

What you will learn

  • Troubleshoot traffic management features such as load balancing, SSL, GSLB and
  • content switching
  • Identify issues with caching and compression
  • Deal with authentication issues when using LDAP, RADIUS, certificates, Kerberos and SAML
  • Diagnose NetScaler high availability and networking issues
  • Explore how application firewall protections work and how to avoid false positives
  • Learn about NetScaler Gateway integration issues with XenApp, XenDesktop, and XenMobile
  • Deal with NetScaler system-level issues
  • Discover the NetScaler troubleshooting tools

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Apr 29, 2016
Length: 270 pages
Edition : 1st
Language : English
ISBN-13 : 9781782175353
Vendor :
Citrix
Concepts :

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Product Details

Publication date : Apr 29, 2016
Length: 270 pages
Edition : 1st
Language : English
ISBN-13 : 9781782175353
Vendor :
Citrix
Concepts :

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Table of Contents

10 Chapters
1. NetScaler Concepts at a Glance Chevron down icon Chevron up icon
2. Traffic Management Features Chevron down icon Chevron up icon
3. Integrated Caching and Compression Chevron down icon Chevron up icon
4. AAA for Traffic Management Chevron down icon Chevron up icon
5. High Availability and Networking Chevron down icon Chevron up icon
6. Application Firewall Chevron down icon Chevron up icon
7. NetScaler Gateway™ Chevron down icon Chevron up icon
8. System-Level Issues Chevron down icon Chevron up icon
9. Troubleshooting Tools Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

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Rampy101 Aug 15, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Good info. Straight-forward and easy to follow.
Amazon Verified review Amazon
Amazon Customer Jan 10, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
covering most of basic troubleshooting steps - get's you started with troubleshooting easy
Amazon Verified review Amazon
Bob Davis Apr 13, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Great reference and how to. Aggregates alot of info spread across multiple sources.
Amazon Verified review Amazon
Amazon Customer Jul 12, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is awesome, all the NetScaler features are covered with deployment examples, flowcharts, Deployment considerations which is very important for admin before starting any project. Highlight of this book is troubleshooting part, all the feature troubleshooting is explained with Wireshark traces and NetScaler counters, which did not find in any book or document in detail as this book.Would like to share chapter wise highlights of this book, which would help buyersChater1:Which covers NetScaler file system, locations of NetScaler system files, configs and Certificates.In this chapter I found “Request switching and connection multiplexing” very interesting and author explained it very nicely, how this feature works and improves the performance of NetScaler.Very well explained about different modes of NetScaler, pros and cons of each mode and when to enable/disable them.Chapter2:Which covers commonly used load balancing methods, when to use which method and what are the factors to consider before deciding the LB type.With respect to troubleshooting he covered how to troubleshoot performance issue( interestingly he did explain how to isolate to specific server/device), uneven load balancing issues, Persistency issues which includes cookie based persistency.SSL certificates and how to troubleshoot SSL related issues .GLSB covered in details, Communication flow from user till backend server, different types of GSLB methods,What is MEP and how to troubleshoot MEP communication related issues.In this chapter I found very useful was, log analysis explained using Wireshark(also how to decrypt the SSL communication) and explanation of NetScaler nsconmsg system counters which I could not find in other books.Chapter3:Integrated caching and compression, how these features helps in improving the user performance.Which are the files/content NetScaler will cache and compress, which is explained very well using flow chart along with sample packet flowWith respect to troubleshooting author explained it very, how to confirm if the severed content is form NetScaler cache or not, what are the HTTP headers to check and NetScaler counters to use while troubleshooting.Chapter4:AAA traffic management which is my favourite topic, in this book commonly used AAA protocols like LDAP, RADIUS,SAML, certificate based auth, Form based and Kerberos.With respect to troubleshooting aaad.debug log which is commonly used AAA troubleshooting is very well explained along with error codes also did point to Citrix article for reference.When comes to cert based auth author explained what is certificate, types of certificate and how they are validated. What to look when authentication failing with NetScaler system counter nsconmsg.Kerberos protocol explanation is awesome which covers deployment options, configuration checklist and authentication flow explained with traces which I did not find in most of the books, this would help admin in implementing an troubleshooting.SAMAL protocol also explained very well with Fiddler traces for better understanding of the flow and what to look when auth failsChapter5:Here comes the mostly commonly used feature of NetScaler, High availability(HA) and Networking.Until I read this book I had lots of confusion about NSVLAN, tagging options, LACP and NIC buffer, all the networking concepts are explained with examples and when to use them.This covers HA in details, ports used by NetScaler in HA, how RPC password plays important role in HA. Different stats of HA and meaning of the same.How to identify the failover event, What logs and counters to check when HA hertbeats are not seen on the devices. Issues caused by ARP, GARP and Split-brain conditions.Last but not least HA syn issues also covered log analysis and NetScaler packet handling with HA is enabled is explained with flow chard for easy understanding.Chapter6:ApplicatioFirwall one of the commonly used App security feature, this book covers Application attacks like cross-site scripting(XSS), SQL injection, Forceful browsing attacks, cookie tampering, Hidden filed tampering. All these are explained with examples and logs, also covers how to prevent them by AppFw policies.Signature based policy configuration is also explained with configuration stepsWith respect to troubleshooting, identifying the firewall blocks using NetScaler output commands and system counters, Also covered performance issues when enabling AppFirewall and how to troubleshoot by creating custom policies.Chapter7:NetScaler gateway is vastly used remote access feature of NetScaler.Difference between basic and smart access modes is covered and when to use them.In this chapter I liked the way VPN session phases are explained using Wireshark captures, phase1:EPA exchanges, Phase2:Authentication exchanges, and Phase3: Authentication exchanges, explanation includes HTTP header/content level details.Troubleshooting includes how to collect client side VPN and EPA logs and how to diagnose the failure.ICA proxy troubleshooting and App launch process is extensively covered in this book• Different phases of App launch process• What are the servers involved in each communication and role of each servers• How to troubleshoot App/Desktop enumeration and launch issues, with sample log analysis and policy hits countersThis chapter also covers the XenMobile(XM) configuration as gateway is used for securing the communication between mobile devices and backend servers.All wizards used in the XM configuration is explained along with inbuilt tools to check the connectivityChapter8:After covering all the network features author did cover system level issues, licensing issues, NTP issues, SNMP issues and how to troubleshoot them.CPU, memory and device hang issues are explained very will using counters and how to read themChapter9:All the inbuilt NetScaler utilities like dashboards, Show techsupport utility are covered, I did find few nsconmsg commands online and was using them while troubleshooting the NetScaler issues but after reading this book I understand the different syntaxes used along with nsconmsg and meaning of the same. Now I don’t need to remember the whole command as I can tweak the command using syntaxes based on the output.
Amazon Verified review Amazon
Amazon Customer May 09, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book shows beginning and advanced administrator all the ins and outs of debugging the citrix Netscaler. From hardware failure detection to networking issues, it's all in there.Dennis van RemortelTech Reviewer of the Troubleshooting Netscaler book
Amazon Verified review Amazon
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