Prior to v13, F5 DNS assumes that all devices in a cluster have knowledge
about all virtual servers, which makes virtual server auto-discovery not
function properly. In this article, we’ll cover the changes to the F5
DNS server object introduced in v13 to solve this problem.
In the scenario below, we have 3 BIG-IPs in a device group. In that device
group we have two traffic groups each serving a single floating virtual
server, and then each BIG-IP has a non-floating virtual server.
Let’s look at the behavior prior to v13. When F5 DNS receives a get
config message from BIG-IP A, it discovers the virtual servers it knows
about, the two failover objects (vs1 & vs2) and the non-floating object
All is well at this point, but then the problem should become obvious when we
look at the status when F5 DNS receives a get config message from BIG-IP B.
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, shown in Figure 1 below.
Since 9.0 was released, TCP payload data (that which comes after the header)
has been consumable in iRules via the TCP::payload and the port information
has been available in the contextual commands
TCP::local_port/TCP::remote_port and of course
TCP::client_port/TCP::server_port. Options, however, have been
inaccessible. Ho... (more)
I got a request yesterday morning to asking if there was a way to drop HTTP
requests if a certain number was referenced in the Accept-Language header.
The user referenced this post on Exploring Binary.
The number, 2.2250738585072012e-308, causes the Java runtime and compiler to
go into an infinite loop when converting it to double-precision binary
floating-point. Not good. Twitter is ablaze on the issue, and there is a
good discussion thread on Hacker News as well. So how do you stop it?
At first, this appeared to be a no-brainer, just copy that string and drop if
found in that... (more)
DevCentral has many rock star contributors. Most are not affiliated
officially with F5 Networks, or DevCentral for that matter, but there are
several F5ers who believe in the community, and really believe in the F5
story. One of those F5ers is Matt Cauthorn, or as you know him in the
community, L4L7. You may recognize Matt as the author of pyControl. Well,
not only did he provide this entrance to a better iControl experience, he has
also delivered in a major way with his Vim plugin for editing iRules
(utilizing pyControl of course to make those calls to BIG-IP). I had toyed ... (more)
Virtualization Expo on Ulitzer
If you haven’t yet downloaded the BIG-IP LTM VE trial, I highly suggest
you do. It is a fully-functional LTM, rate-limited to 1Mbps throughput.
If you’re not familiar with virtualized environments, hopefully this blog
will fill in some blanks for how to get started on the network front.
Before downloading your VE image, you need to choose what virtualization
environment you’re installing into. The supported options in the type 1
hypervisor are VMWare ESX version 4 and ESXi version 4. For the type 2
hypervisor (requiring a host O... (more)