Archive for November, 2010

Hi all,

I’m back. I didn’t really go anywhere, but I’ve been too busy writing up my latest assignment to bother with such frivolities as blogging up the place. Respec.

So I have 4,000 words to play with. Three sections:

  • Part 1) Network design and implementation, 40% of the overall mark
  • Part 2) HACME network performance tools, 20%
  • Part 3) HACME security audit, 30%
  • Added value: 10%

By my reckoning that means 1600 words, 800 and 1200 respectively, plus a little in reserve for good times. So what do I do about that then? My Part 1) is already 5000 words and I barely said a thing. Part 2) 4000 words. Part 3) 5000 words. And I’m pretty good at précis writing (believe it or not).

Gah! I’m gonna have to slice up this bad boy to buggery and put all the less-great-than-other-great-stuff in the appendices. Damn you, mathematics!



ReBirth on the iPad

Posted: November 16, 2010 in Music

I remember it well…

It was around 1997. The old mod and demo scenes were coming to an end. Screamtracker had had its day, and the internet was abuzz with new and fantastic ways of making music on your computer. Unfortunately I didn’t have the gear or enough money for software like Reason, so my youthful passion for making computers make cool sounds had stalled.

Then I happened upon a cover CD from an computer magazine and on it was this thing called ‘ReBirth RB-338’. It was a PC program which emulated the classic 80s synths and drum machines: 303, 808 and 909. It couldn’t possibly be any good, could it?

It was amazing. The noises you could get out of this thing were just awesome. Its two 303s sounded exactly like real 303s but without the massive price tag. Thumping, penetrating bass lines which you simply couldn’t reproduce any other way. The 808 and 909 emulators were good too, included more for convenience than anything, but they totally added to the experience.

Then I forgot about ReBirth RB-338.

Then I remembered about it again! A few months ago I grabbed a fresh copy of it and was…disappointed. The sound was still as great as ever, but the tiddly interface and awkward usage made me wish I’d left it to memory. “How great would this be on the iPad?” I thought. Multi-touch is what ReBirth needed, a lick of paint and the ability to export songs and patterns for external use.

Propellerhead software had released a cynical iPhone port of ReBirth but it suffered with the same problems that the desktop version was plagued with. But then…

Lo and behold! Yesterday I checked the App Store and I saw that they had released an iPad version of ReBirth. Grabbed it. Love it. It’s awesome. I did this in an hour, and it’s freakin’ amazing. The software, that it, not the song. The song needs a lot of work – it’s just a collection of cheesy ideas. But you can see just what ReBirth is capable of:

You can still download the PC and Mac versions of ReBirth for free from here: But they’re starting to show their age. The interface isn’t that good by today’s standards and it can be tricky to export the output for use in other packages.

The iPad version of ReBirth gives it a new lease of life, building on a still thriving community. Simply, it’s the best app on my iPad, and it will burn many, many hours of my time. Like now, for instance, when I should be working but instead I’m eulogising about an ancient piece of software which a multi-national company has dusted off a little and is selling for a cynical mark-up. But I don’t care. It’s awesome, and well worth the £8.99 it costs.

And do you know what’s even better than that? Korg has just released an iPad emulator of their ubiquitous analogue synth sound – the iMS-20. Must…resist…too…many…distractions…

I’m surely gonna get it, but I will wait until my assignment is finished :)

1) Install the Microsoft Loopback Adapter as per this guide (Windows 7. Similar process for other Windows versions):
2) Configure the Loopback Adapter with whatever network settings you like
3) Restart the PC. You cannot continue until you restart the PC.
4) Open up a cmd prompt as administrator and navigate to your GNS3 installation directory, something like this:
D:\Program Files\GNS3\
Run this batch file:
Network device list.cmd
It will come up with something like this:
d:\Program Files\GNS3>”Network device list.cmd” 

Network adapters on this machine:

Name      : Local Area Connection* 13
Desciption: Anchorfree HSS Adapter

Name      : VMware Network Adapter VMnet1
Desciption: VMware Virtual Ethernet Adapter

Name      : VirtualBox Host-Only Network
Desciption: Sun

Name      : VMware Network Adapter VMnet8
Desciption: VMware Virtual Ethernet Adapter

Name      : Local Area Connection
Desciption: VIA Rhine II Fast Ethernet Adapter

Name      : Loopback
Desciption: MS LoopBack Driver

Find your loopback adapter and take note of the last few characters of the long code (i.e. 6861 in this example).

5) Run GNS3 as Administrator.
6) Add a Router and a Could.
7) Configure the Cloud. On the NIO Ethernet tab find your loopback device on the dropdown
Add this and return to your project.
8) Start the router and configure it with an IP address which could talk to the one you set on your loopback device.
interface FastEthernet0/0
ip address
duplex auto
speed auto
That’s it! Ping from the router to your desktop and vice versa to prove connectivity. You can now use GNS3 and Dynamips as real routers on your home network, and can make VMs talk to your virtual routers, enabling you to perform network monitoring at home without needing lab access.

I chose to use PuTTY for my console access because it’s the one I’m most familiar with. Here’s how I set it up:

Just to prove that GNS3 and Dynamips is working correctly I put together a really simple network with dynamic routes using OSPF. Got it talking within minutes, which is great news. However…

…Dynamips is too resource-hungry for my old PC. It uses all my CPU all the time, making it impossible to build a sizeable network in my environment.
Today I will undertake a simple experiment to achieve something that’s impossible in Packet Tracer: prove that HSRP works. (Packet Tracer 5.3 doesn’t support HSRP.) This means that R4 and R5 are equivalent to each other and one can take over is the other fails. They have their own IPs but share a HSRP IP address. It is this address which is used by the rest of the network, meaning that other devices don’t need to be configured in the event of an R4/5 failure.

Simple network where R4 and R5 should be in the HSRP pool, and R6 wants to communicate with one of them
R6 has the higher priority so gets all the load while it is available. The above screenshot shows each router’s config. I have proven complete communication between all three.
IP sits in front of and
Experiment by switching off R4: R5 takes over.
Switch off R5: no service
Switch R4 back on again: we get a response again. Success!
Simple, but it shows how easy it is to build in resilience, assuming you have the money to double up your devices. Other things to think about are the cables. There’s (may be) no goo building resilience into your devices unless you have resilient power and communication lines. The old classic ‘man in digger breaks your cables’ scenario would take out everything to the left of the switch unless you had an alternative physical route. Same is true for power: if R4 and R5 use the same power source and that goes down, what benefit did you gain by having resilient devices?
Another issue would is configuration management: R4 and R5 need to be kept in sync at all times for failover to work seamlessly.
This is a good example of how to build simple resilience in a small network, but on a large scale you’ll be thinking about GLBP or dedicated hardware load balancer devices.
Tomorrow I will hook up Dynamips to my local network and show how my VM devices can communicate with each other via my virtual Dynamips devices. But I will leave GNS3 after this because it’s just too slow on my computer.