Simon PainterSomewhere to keep things

Networks

Bits & bytes

You have probably been directed here because you sent me an email with data volumes quoted in GB/MB/B or Gb/Mb/b inconsistently. Don’t worry, it happens all the time; so often in fact that I wrote this blog post to explain why the difference is important. Network people measure traffic (or bandwidth) in terms of bits […]

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Sergeant Clip Review

Full disclosure: I received some free samples and have worked with the inventor at a former employer. I don’t have any financial interest in the product though. I was quite excited to get my Sergeant Clip samples through as the inventor had told me about them in the past and I have been involved in […]

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The best ‘bug’ I have ever seen…

Way back in October 2013 Cisco slipped out this little field notice to customers and engineers across the globe. The position and function of the mode¬†switch is such that it can be pressed by the protective boot on certain types of cables and cause a reset to factory settings. Problem Description Certain types of snagless […]

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Route summarisation

I found a very clever site that does route summarisation from a list. This is ideal if you dump out a copy of your routing table and want to see where the routes can be summarised. It’s also useful if you have subnets for a firewall rule that you want to consolidate. http://www.netmatics.net/FreeTools/IPv4SupernetTools/SupernetCalc

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Getting your underpants inside out over NAT

A colleague asked me to write a post on NAT and so this one is for him. I’m going to use a very basic three router lab to go through the common types of NAT and where they are used. First off there is the convention of inside and outside interfaces.¬†The golden rule here is […]

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Logical look at masks

Having done an introduction to wildcard masks and the cool things you can do with them I thought it might be worth writing about the logic behind both subnet masks and wildcard masks. Masks use two of the most basic logical functions that computers can perform, a logical AND and a logical OR. Logical AND […]

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Getting Wild[card masks]

If you ask most people what a wildcard mask is they’ll probably say it’s an inverse subnet mask. That is a massive under-representation of the power of a wildcard mask and does not do fair justice to the range of useful tricks you can do with a wildcard mask. We’ll start with why people think […]

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