Hue-ge pain in the butt

I have a Philips Hue bridge which lets me control the lights in my flat in a variety of useful ways. It’s a good bit of kit, but with one major problem – it assumes you’re running PAT (Port Address Translation), and that your Hue bridge and the device you access https://account.meethue.com/bridge both access the Internet from the same source IP address. If not, even though the devices may be in the same broadcast domain and the same IPv4 subnet, you won’t be able to link your Hue to your account.

Despite tweeting for assistance, I ended up crying shibboleet and reverse-engineering the method of linking they’re using. Here’s what I found out, in the hope it’ll save somebody else a lot of time.

My Internet services are through the excellent A&A, and I can’t recommend them highly enough. I have a public IPv4 subnet, and each of my devices accesses the Internet without any address translation. Inbound connectivity is restricted – there are only a few things I need accessible from the Internet. (As an aside, I have two DSL lines, with my IPv4 subnet routed down each – load balancing and resilience)

My Hue bridge connects to https://discovery.meethue.com/, and that service makes a note of an inventory that the bridge sends to it. Here’s where the problem is – visiting discovery.meethue.com only returns the devices that registered from the IP address you’re connecting from. That’s fine if all your devices go through address translation and appear to come from a single external IP address, but useless for me – my mobile device uses an entirely different IPv4 address, as does my desktop and laptop. The Hue app reports that no devices were found.

After some frustrating interactions on Twitter, I solved the problem myself. I set up IP Masquerade – essentially port address translation behind the router’s external IPv4 address – for my Hue bridge and my mobile device, so they’d appear to be coming from the router’s external IP address. Rebooting the Hue, disabling one of the PPP connections on my router (necessary since they both have an IP address assigned, and my outbound traffic is load-balanced per TCP connection) and linking the device from my mobile phone then worked. Rolling it all back and rebooting the Hue again leaves the device linked to my account.

What a mess. Adding a “Enter the IP address of your Hue then when prompted, press the button” on the device linking page would have been a whole load easier. Not everyone’s Internet connection is the same, nor is everyone as experienced in network engineering as I am… yet still it took me three days to work out a fix.

In summary: buy Hue devices – they’re good, but beware if you’re doing anything that possibly deviates from the common case.

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