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Frequently Asked Questions About F5 Technology

F5 is the creator of and home to many different, powerful technologies. We offer some of the most powerful, advanced application delivery technology in the world. As with any advanced technology, however, there are often times terms and names... Read more
0 Reviews

Security Irules 101: DNS Gravitational Disturbance

Introduction iRules are a powerful tool in the F5 administrators arsenal. They allow administrators to adapt and customize the F5 to their needs. They provide extensive power for security engineers as well. We’ve decided it’s time to revisit... Read more
1 Review

DevCentral Architecture

Everyone has surely (don’t call me Shirley!) at least been exposed to THE CLOUD by now.  Whether it’s the—I’ll go with interesting—“to the cloud!” commercials or down in the nuts and bolts of hypervisors and programmatic interfaces for... Read more
1 Review

iRules logging to multiple locations with ease

Some months back I was at an account where we were developing some iRules to provide logging detail. One of the complications was that some of the infrastructure to support remote logging was in the process of being implemented and was not... Read more
1 Review

iRules Concepts: Logging, a Deeper Understanding

Multiple times in recent iRules presentations, whether on the road or here within F5, there have been questions raised when the topic of logging within iRules gets brought up. Specifically people are curious about logging best practices,... Read more
0 Reviews

Redirects, Rewrites and App Transfers via iRules

While traveling and talking about iRules, I come across a wide variety of topics that people are looking to address. From security offload to custom routing to just about anything you can think of. This week, while out and about at User Groups, I... Read more
2 Reviews

iRules Concepts: Tcl, The How and Why

F5 uses Tcl as the interpreter for iRules. Many people often ask why that is. This questions is usually followed up by an immediate, "Why not Perl?" or "Why not Java" or "Why not ?". I understand the question, and... Read more
Average Rating: 4.5
5 Reviews

v11: iRules Data Group Updates

Several months ago I wrote up the v10 formatting for internal and external datagroups: iRules Data Group Formatting Rules. In v11, however, there is a change to the format of the internal data group and the data group reference to external class... Read more
Average Rating: 4.6
11 Reviews

iRules Concepts: Connection States and Command Suspension

Within iRules, in addition to mastering the language syntax and tricks therein, there is an added layer of understanding that can help in taking your iRules fu to a whole new level. Connection State. Connection states are relatively simple i... Read more
Average Rating: 4.9
3 Reviews

v11.1: DNS Blackhole with iRules

Back in October, I attended a Security B-Sides event in Jefferson City (review here). One of the presenters (@bethayoung) talked about poisoning the internal DNS intentionally for known purveyors of all things bad. I indicated in my write-up tha... Read more
Average Rating: 4.9
3 Reviews

v11.1–Add Signatures or Checksums to iRules via an iApp

iApps, introduced in v11, have a primary function in controlling the object creation and management for an application delivered by BIG-IP. As discussed previously, however, anything that can be accomplished in TMSH can be done in an iApp, so wha... Read more
1 Review

v11.1–External File Access from iRules via iFiles

New in BIG-IP version 11.1 are iFiles, a feature that allows users to load files through tmsh or the GUI onto the BIG-IP which can be referenced from iRules. This has an immediate use case of supplanting several of our codeshare entries for sorr... Read more
Average Rating: 4.9
8 Reviews

Base32 Encoding and Decoding With iRules

Introduction Anyone that's done any amount of programming has probably encountered Base64 encoded data. Data that is encoded with Base64 has the advantage of being composed of 64 ASCII characters, which makes it portable and readable with... Read more
0 Reviews

APM Session Invalidation Using ASM

Introduction: Whenever customers expose their internal resources on the Web using VPNs or SSL VPNS there is still some concern over what type of traffic comes through the connection. In order to assist with these concerns we can provide a combine... Read more
Average Rating: 4.9
3 Reviews

Cookie Persistence and Troubleshooting

The BIG-IP persistence cookie is a valuable configuration option that allows stateful applications to remain persistent to a specific node with no additional configurations within the application or on the server(s) by doing something lik... Read more
2 Reviews

iRules Concepts: Considering Context part 2

In part 1 of this brief series we talked about what context means while coding, how it affects our perception of things and the different contexts within iRules that are inherent and would be covered in this 2 part-er. As a refresher, those... Read more
0 Reviews

iRules Concepts: Considering Context part 1

Language is a funny thing. It's so easily misunderstood, despite the many rules in place to govern its use. This is in part, of course, due to dialects and slang, but context shouldn't be underestimated as an important piece o... Read more
0 Reviews

iRules 101–#18–Revisiting the TCL Scan Command

I covered the Tcl scan command back in the iRules 101 – #16 – Parsing Strings with the TCL Scan Command, but this example (by Hoolio, who else?) was too good not to share with the community. The request involved parsing a log entry as efficientl... Read more
1 Review

Link Tracking With iRules - Part 3 - URI Filtering

This is the third article in a series on building link tracking functionality with iRules.  The previous articles were Link Tracking With iRules - Part 1 Link Tracking With iRules - Part 2 - Filtering Results In the first article, ... Read more
0 Reviews

Multiple Certs, One VIP: TLS Server Name Indication via iRules

An age old question that we’ve seen time and time again in the iRules forums here on DevCentral is “How can I use iRules to manage multiple SSL certs on one VIP"?”. The answer has always historically been “I’m sorry, you can’t.”. The... Read more
0 Reviews

iRules IP Comparison Considerations with IP::addr Command

Anyone utilizing IP network comparisons in iRules is probably familiar with this syntax: 1: if { [IP::addr [IP::client_addr]/24 equals 10.10.20.0] } { 2: ##Do this 3: } In fact, there are several methods for doing a... Read more
Average Rating: 4.9
3 Reviews

iRules Data Group Formatting Rules

BIG-IP LTM supports internal and external classes (called Data Groups in the GUI) of address, string, and integer types.  An internal class is stored in the bigip.conf file, whereas external classes are split between the bigip.conf and the... Read more
Average Rating: 4.5
6 Reviews

Accessing TCP Options from iRules

I’ve written several articles on the TCP profile (click here) and enjoy digging into TCP.  It’s a beast, and I am constantly re-learning the inner workings.  Still etched in my visual memory map, however, is the TCP header format, show... Read more
Average Rating: 4.9
5 Reviews

Link Tracking With iRules - Part 2 - Filtering Results

A common request from application developers is the ability to track the popularity of different areas of their applications.  This could be which app is most popular or which image is linked to most often.  Analytics packages such a... Read more
0 Reviews

Help Kill IE6 with iRules

For those that haven’t gotten the memo yet, IE6 is on its way out. I know this has been something developers, myself included, have been hoping for for quite some time now. IE6 is old and frankly doesn’t offer the support needed by far too man... Read more
0 Reviews