bang

If you’ve ever set up DNS forwarding on a Ubiquiti EdgeRouter and have your own internal authoritative DNS servers, then you may have noticed that it doesn’t quite work right. If you look up the hostname of your router via the EdgeRouter, you’ll always get back an address of 127.0.1.1.

WTF?!

The Problem

EdgeOS makes use of dnsmasq for its DNS server needs. For the most part this works well and is very flexible. It allows you to set up a cached DNS forwarder and do all sorts of nifty DNS routing. Unfortunately, the default options are a little wonky.

By default, dnsmasq will read /etc/hosts and use what it finds there to answer DNS queries. While this may be good for some scenarios, it’s terrible in others. For example, the edgerouter adds default hosts entries for the router itself, that look like this:

Due to the dnsmasq options, it picks these up and will always answer queries for the router’s hostname with an unreachable loopback IP address.

Because there’s no place like 127.0.1.1…

The Fix

Dealing with this is thankfully simple. Just turn one option on, and you’re set:

This sets the –no-hosts option on dnsmasq, which prevents it from reading /etc/hosts at all. Now your DNS forwarder will completely ignore anything it finds in there and simply forward the request to your configured DNS servers. It’s also worth noting that the DHCP/DNS integration works through a different mechanism, so that will still work just fine if you choose to use it.

The other suggestions I’ve seen involve setting interface parameters to force a static DNS mapping, but this has the advantage of forwarding the DNS request to your actual nameservers.

Hopefully this will help someone out there. It’s been annoying me for a few days now as I set up my folks’ network…

Sensative Strips are thin devices that you can install on a door or window to detect the open or closed state. They’re small, they’re functional, and amazingly enough, they speak Z-Wave. Install one on the frame of your door, and you have a nice little sensor without having to run wires.

I got mine from a seller on Amazon.

They’re also fiddly little things, at least when pairing with OpenHAB…

I’m mainly looking at OpenHAB for support of the advanced functionality in the HomeSeer HS-WD100+ in-wall dimmers. Specifically, they have multi-tap functionality supporting four commands in addition to the generic On/Off function. For example, my pool light switch is out by the shed; wouldn’t be nice if I could just double-tap the switch at the back door instead?

Here’s one way of making it work in OpenHAB 2…

TUN/TAP Demystified

May 21, 2016

Have you ever wondered what the Linux TUN/TAP driver is for? Wonder no more! After spending most of last weekend tweaking the NuttX Simulator network support, I now have a pretty good idea of what TUN/TAP is, what it’s useful for, and how it works.

Might as well pass it on, right?