Chromecast causing wifi interference – resolved

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Summary: I’ve found Google’s Chromecast to be a great streaming device but in rare cases it can misbehave and cause wireless access issues.

I bought my first Chromecast the day they were released in the UK (March 18th 2014), totally by chance, and I’m a big fan. Once setup they’re simple enough to use that my 2yr old son can now use a tablet to power on our TV and watch a program of his choosing via BBC iPlayer or Plex without any help from me – and that’s something my in-laws can’t manage. I’m not sure it’s socially a good thing but at least the technology works!

Chromecast wifi analyzerHowever I have noted a few issues, notably with their use of wifi. When you first plug in the Chromecast it’s in ‘master’ mode which means it acts as an access point, thus allowing you to join its wireless network with a tablet and configure it (and also opening up at least one vulnerability). Once the initial setup is complete however it’s supposed to go into ‘managed’ mode which means it should stop being an access point and act only as a wireless client but mine was still intermittently acting as an AP and therefore causing interference, as seen by Wifi Analyser (highly recommended by the way). In my case (and for others too) I saw additional wifi signals, always on the same channel as my home wifi, and the signal strength was greater than my home wifi when I was near the Chromecast. The Chromecasts didn’t broadcast an SSID (it showed as ‘?’ in Wifi Analyser) with a MAC address starting in fa:86:ca, which belongs to Google (although none of the OUI lookup databases seemed to know it).

This useful article about how Chromecast uses the Wifi network, including packet captures, goes into some possible causes although it’s been 18 months since the Chromecast was released and firmware updates may have resolved some issues mentioned.

How do I fix it?

The fix, at least for me, was a factory reset of the Chromecast – hardly worth of a blogpost! However I’d ‘reset’ mine several times by simply going into the Chromecast utility on an iPad (or Android tablet) and after a reboot I’d go through the setup again (inputting wireless password, naming the device etc) and that DIDN’T fix the issue. A factory reset can be done by holding down the power button on the Chromecast for 25 seconds until the light on the device flashes or via the Chromecast app (detailed walkthrough here).

It’s also worth checking that it’s running the latest firmware (31432 as of May 22nd 2015, according to Wikipedia) – it should update automatically (and in fact you can’t stop it doing so which isn’t ideal) but sometimes a factory reset gives it the kick up the proverbial it needs to update. If you need help the official Google Chromecast forum is a good place to start as is the online troubleshooting wizard.

8 thoughts on “Chromecast causing wifi interference – resolved

  1. Turns out that my Chromecast (v2) does this unless you turn off Guest mode. Mine didn’t broadcast SSID either, and used the same channel as my main WiFi. Not great.

  2. I had a similar problem and did a factory reset. When I started to set up the Chromecast again I had a screen that enables guest mode, I disabled guest mode and the Chromecast SSID disappeared.
    Seems to have cured the problem but time will tell.

  3. Interesting article. Thank you for posting this.
    I have exactly the same problem with my Chromecast Audio, bought late 2015.
    Once set up, it continues to broadcast a strong signal on one wifi channel (currently channel 11, but I have seen it skip between channels 6 and 11).

    Unfortunately, the factory reset did not work for me, and after setting up afresh, my Chromecast Audio continues to broadcast, making my wifi network somewhat problematic (largely because my network is using channels 6 and 11 which are the best for me given the other wifi routers in neighbouring houses).

    I guess I will have to keep looking for an answer, but will post if I find a solution in case helpful for someone else

    1. Ah. Turns out that if you have guest mode switched on, it continues to broadcast its own wireless network. Turning off that option fixed it for me.

  4. I have 3 Chromecast (2 first gen and 1 second gen). All three exhibited the problem mentioned even after multiple factory resets. A call to Google tech support informed me that this behaviour is “normal Chromecast operation”. After some experimenting, I uncovered the solution mentioned by others, namely, disabling Guest mode.

    Thanks for posting this article. I should have read the comments before dashing off to try the factory reset procedure.

    – David

  5. We tried the factory reset and disabled guest but it still keeps showing Chromecast as a WiFi network and when it is on (it comes and goes multiple times a day) it disables all of the WiFi in the home! please help

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