Preamble
I have 2 Roku devices. The living room device is direct connected to the telco boundary router. This is so that my playing with things will not disrupt the spousal TV time…
The 2nd one (“mine”) is connected via a very high speed link (5G? Something like that…) to an internal house WiFi router that then has a hardwire uplink to the telco router. This puts 2 NAT (Network Address Translation) conversions between my TV and the provider.
The Experience
So this morning I was checking the weather. Well, really, I knew what the weather was as I stepped outside. I was checking what the various weather apps on the Roku said was the weather.
First off, I noticed Wunderground said “Today will be hotter than yesterday” yet it’s colder so far and the number they predict doesn’t look like much. Second, they were showing the “now” temperature as a degree F higher than the other two.
Next I went to Weathernation and Weather4us. The Weathernation folks correctly stated “fog and light mist” or some such. It is, in fact, a touch foggy and dank at the moment. In my experience, they are more right (and typically cooler) than Wunderground.
But it was the Weather4us that got me posting. Not for any weather data, though.
See, Weather4us is mostly just some data panels. It also starts off with a single commercial (to book some revenue before you scan ‘it is cold and dank’ and hang up to go get a coat…) But it didn’t. No commercial.
I’d noticed already that another ‘ad’ was gone. The Roku puts up a columnar list of channels to choose, and has a fake BillBoard on the right side. A large area with pictures of footlights at the bottom. In this they stuff an advertisement for some upcoming show. Like a poster on a wall. (i.e. not animated). This panel has been gray on “my TV” since I swapped to the 2 router connection.
My hypothesis
What I think is going on here is that the double NAT breaks “push” advertising. The App can still suck down pull adverts, and any “in stream in the content” ads still run, but an ad pushed from the center can’t find it’s way back through the NAT routers. Sent to a port and IP at the Telco Router, the telco router will send it on to the interior router (or the living room TV) as they have a translation table entry, but that interior router has no outgoing connection mapped for that particular communication, so blocks the inbound push. (NAT opens a translation table for your outbound, and then accepts inbound replies to things it has sent out.) Somewhere in the double NATing, a key number gets changed and then push packets can’t find their way back to the inner device.
Nice that.
At some point I need to actually look at who is dropping what kind of packets and get the details straight, but it just isn’t a priority at the moment.
All I really need to know is that 2 layers of NATing routers is not only good for security, It also looks like it blocks push advertising too. At least some forms of it.
Musings from the Chiefio 
Noted.
Double “NAT” translation to be added in the tool box.
Blocks Ads?
SOLD!
Just curious. Do you get youtube ads with your double-NAT setup? I ask because I don’t get them at all in Firefox, which I have configured to run in private mode. I get all the youtube ads in Safari, which runs in non-private mode. Ergo, Firefox is my youtube browser of choice.
I should have said it a bit differently: I only watch youtube in Firefox and that is all that I use it for. I use Safari for all other youtube browsing because the user experience in normal usage suffers when private mode is used.
I still get all pull ads, except for those my DNS list blocks. For Youtube I’m using chrome but I think I may have an adblocker turned on, so most ads are gone. It’s been a few years since I set up the chromebox and I don’t remember exactly what all I configured on it.
Doing a quick test with the tablet, the embedded commercials are still seen in Youtubes.
Do realize, the dual NAT doesn’t block most ads, only the push traffic that isn’t the dominant form. It’s only one small set that is blocked this way.