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Well we’ve made it to the end. This is the 10th and final installment of #The101: iRules. So far we’ve talked about everything ranging from the very basics of programming concepts to some more particular iRules type concepts such as events and string manipulation. Hopefully you’ve been following along and garnered some good bits of information along the way. For those that may just be catching the series, or those that could use a refresher, I’ll list out the articles in ...
articleadnnewstechtiptutorial October 11, 2012 by Josh Michaels
Sorry, I’ve been monkeying around on the twitter birds, following one of my favorites, SecurityHulk. https://twitter.com/securityhulk Follow, read, laugh, cry, and ponder the Green Wisdom.   Anywho, todays fun to be had is SSH.  I’m going to skip the history lesson (here) and summarize.  SSH gives us a secure connection into a location, providing confidentiality and integrity.   Primary usage is accessing a remote command line, but you can do so much mo...
So far in #The101: iRules we’ve covered some pretty varied topics. Everything from a primer on programming terminology to iRules Events and why they’re important has been discussed so far. If you haven’t been following along, or if you need a refresher, here’s the complete list: iRules: Introduction to Programming & TCL Introduction to F5 Technology & Terms Introduction to iRules Events & Priorities Control Structures & Operators Variables In this s...
articlebig-ipnewstechtiptutorial July 11, 2012 by Colin Walker
One of the many things that I talk about quite often when presenting about or discussing iRules is troubleshooting and testing. Mind you these are two different, yet similar things. The difference is basically whether things are pre or post deployment, but the idea is the same. In both cases you're basically looking to figure out if your iRule is working, and if not, you want to figure out why. To do this there is no magic button, rather there is a process to go through, a bit of a logical loop ...
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, performance impact, when to log or not, and how to ensure they're not bogging down their device while still recording the necessary data. As such, it seems like a pertinent topic to demystify a bit by way of background and explanation. First, to understand ...
articlestoragenewstechtiptutorial February 29, 2012 by Jim McCarron
Summary 8.3 names are a relic of the 1980’s, when the FAT12 and FAT16 file systems used in MS-DOS did not have a provision for arbitrarily-long filenames. In those days, names could have at most eight characters, followed by a single period, and up to a three character extension. That was 25 years ago. More than a decade ago, 255 character names were introduced in Windows 95 and NT 3.5. These operating systems included a slot in their file systems for an “alternate name” formatted according t...
There are so many things that you can do with iRules that it can be pretty staggering to narrow down what the "most useful" commands are, but if I were given that task and absolutely had to, I would say that DNS resolution ranks up there pretty high on the most powerful list. Perhaps not as widely used as the HTTP or string commands, but the times that it does get used it solves problems that simply couldn't be solved any other way, often times. Whether it's querying an address before routing tr...
articlestoragenewstechtiptutorial September 30, 2011 by Bill Minckler
Introduction The ARX has many features for controlling file placement between the servers behind the ARX. ARX File Placement Policy (policy) has many configuration options that allow for fine tuning the behavior of rules. Under most circumstances keeping the configuration simple (using the default values) is the best approach. This Tech Tip discusses some of the more common features used by place rules and explains how to use the features more effectively. Problem Statement When configuring ...
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 comparison.  Here are three functional equivalents that include the most common form shown above: [IP::addr [IP::remote_addr]/24 equals 10.10.20.0] [IP::addr [IP::remote_addr]/255.255.255.0 equals 10.10.20.0] [IP::addr "[IP::remo...
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 file system (the class itself is defined in the bigip.conf file, but the values of the class are stored in the file system in a location of your choice, though /var/class is the location defined for synchronization in the cs.dat file)  Which flavor?&...
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