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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