More numbers than you can shake a stick at. Just to give you an idea, at the ISP level (/32) that’s 79 septillion IP addresses assigned. That number is so big I had to go look it up on Wikipedia to find out what it’s called. Every home user will have 18 quntillion addresses at [...]

Folks, domain names are a subscription service. That means you have to pay to keep them every so often. You don’t pay for them once and keep them forever. If it’s a .com, you most likely have to renew it every year and it’s a lot like your Time magazine subscription: If you don’t pay [...]

Want to limit the total bandwidth available to a Linux server, and don’t want to do it at the switch or router? Here’s how!

The Spamhaus DROP list (Don’t Route or Peer) is still awaiting it’s BGP feed for network providers. So in the meantime, I’ve knocked up a little PHP script that downloads the DROP list from Spamhaus and spits out either a list of IPtables rules or a Cisco access control list. View Source: http://www.potato-people.com/code/misctools/spamhausdrop.phps Download: http://www.potato-people.com/code/misctools/spamhausdrop.tar.gz

MTR, also known as Matt’s Trace Route, is an enahanced traceroute utility which after making the initial run continues to rerun the traceroute and calculate hop-specific packet loss and latencies.

Unfortunately, virtually everytime someone calls me and mentions “packet loss” and “MTR” in the same breath, it’s because they do not understand the output.

A few further thoughts on things that people forget to take into account when attempting to measure bandwidth: When measuring bandwidth, attempt to use a site or tool that is close to your ISP. If you’re in the UK and you try to test your connection using a site hosted in the US it’s never [...]

As I work in a ISP, I (unfortunately) have to deal with the abuse mailbox. And unfortuantely, these means responding to DMCA notices from US companies. How do you deal with a copyright infringement happening on your network, but when the holder is in the US and trying to apply US law? DISCLAIMER: I am [...]

An issue that comes up for me at work time and time again is customers misunderstanding how bandwidth is measured.

A common problem with ADSL in the UK is that most connections are still using PPPoA. This means that if you want a computer to have a public IP address on one of these connections, you need to either have a block of IP addresses routed by your ISP to your router (at extra) cost, [...]

The most common attack vector on Linux web servers, is to get something uploaded onto the server that can then be executed. Most of these automated attacks try to put their payload into /tmp, which is universally writable by any user, and then execute it. But what if they couldn’t execute it?