Links I find useful

My list of links that have been useful to me in the past and I keep returning to them.

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Making a GPU with an 8 pin work with a 6 pin power

Recently I had to swap my good old power supply for a spare one. However, I needed an 8 pin GPU power connector and the spare PSU had only a 6 pin. Turns out 6->8 pin conversion is not that hard to do.

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Controlling a SIM800L modem

My quick notes regarding a SIM800L module on an inexpensive SIM800L EVB “SIM800LV2.2” carrier board from eBay. Communicates happily with a computer through a generic USB<>TTL converter, 5V logic levels and 5V power at 9600 baud. Carrier board includes a TTL level shifter and 2 diodes in series to drop the voltage from 5V to ~3.6V.

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Fun with .arpa domains

As you may know, .arpa domains are used for reverse DNS. But did you know that they are usable for forward DNS too?

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ECMP on Linux

During a new server deployment I’ve come across the need to use ECMP on Linux. Turns out it’s actually really simple to configure. Read More

Bird Unreachable Routes on multihop BGP Sessions

In the past few months, quite a few people have asked me this question: “I bought a VPS from provider X, turned up a BGP session with them and my routes are all marked unreachable”. Today’s post will hopefully shed some light on what causes this phenomenon and how to deal with it.

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Backing up OVH Public Cloud instances using snapshots

OVH Public Cloud platform is based on OpenStack software. As such, it has an API using which many procedures can be automated. Today I will be showing how to automatically create whole server backups using snapshots.

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Configuring Tunnel Broker BGP on Mikrotik

Hurricane Electric’s free service Tunnel Broker allows one to set-up 6to4 tunnels in order to get IPv6 connectivity to IPv4-only sites. In addition to “regular” tunnels, where they assign you a random prefix from their ranges, they also support BGP┬átunnels. Today I will show you how to set one up and configure it on a Mikrotik device.

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Postfix: Routing outgoing email based on sender domain

I was in a situation where I needed to implement a mail routing policy: Outgoing email from a specific domain gets routed through a relay (eg. Amazon SES) and all other goes directly.

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Compiling nginx with PageSpeed and naxsi

Today we are going to compile nginx web server with naxsi WAF (Web Application Firewall), Google PageSpeed modules and HTTP/2 support.

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