AT&T Fiber in the SF Bay Area is flipping bits • Hacker News Board

Re: AT&T Fiber in the SF Bay Area is flipping bits

#371

Post by _rs » Wed, Dec 09, 2020, 5:05 AM UTC

warent wrote: post #356

_rs wrote: post #244

Earlier quoted context omitted.

So are you bridged then or is it really a double nat?

this is really where my limited knowledge of networking shows. I'm not entirely sure but I want to say both or double nat. There's two networks, but my router thinks theirs is a modem and is connected via the "Internet" port, not just a normal device port

Ah ok - sounds like a double NAT then, not a bridge.

Edit: to go into more detail, their router is acting as a NAT for your public IP, giving you your first subnet, and then your router is getting a single IP on that subnet and creating a NAT where your devices all get IPs. In a bridge there would only be 1 IP space behind a single NAT. In your case with a double NAT a lot of consumer things might not work (like UPnP) and port forwarding would require you to add rules to both routers.

Re: AT&T Fiber in the SF Bay Area is flipping bits

#372

Post by [deleted] » Wed, Dec 09, 2020, 6:40 AM UTC

ericbarrett wrote: post #370

noncoml wrote: post #355

Earlier quoted context omitted.

I think you are confusing the IP header with TCP header. Routers don’t touch the TCP header at all

No. URG, “Christmas tree” packets, etc. all can be mangled by the ISP. Or more commonly dropped

[deleted]

Re: AT&T Fiber in the SF Bay Area is flipping bits

#373

Post by warent » Wed, Dec 09, 2020, 9:10 AM UTC

_rs wrote: post #371

warent wrote: post #356

Earlier quoted context omitted.

this is really where my limited knowledge of networking shows. I'm not entirely sure but I want to say both or double nat. There's two networks, but my router thinks theirs is a modem and is connected via the "Internet" port, not just a normal device port

Ah ok - sounds like a double NAT then, not a bridge. Edit: to go into more detail, their router is acting as a NAT for your public IP, giving you your first subnet, and then your router is getting a single IP on that subnet and creating a NAT where your devices all get IPs. In a bridge there would only be 1 IP space behind a single NAT. In your case with a double NAT a lot of consumer things might not work (like UPnP…

Thanks, yes that's exactly what it is then. In order to give external access to my devices (e.g. my NAS) I have to forward ports from their router to my router, and from my router to the device. So, definitely double NAT. Amusingly the person who installed it incorrectly called it a bridge.

Thank you for the insight and lesson!

Re: AT&T Fiber in the SF Bay Area is flipping bits

#374

Post by Rapzid » Wed, Dec 09, 2020, 6:12 PM UTC

jlgaddis wrote: post #268

Rapzid wrote: post #232

Earlier quoted context omitted.

I have ATT fiber in Texas and was having issues recently, probably for a few days, where DNS props would just fail(I use Google's DNS), huge pauses in page loads with the occasional just doesn't. Happened over the long weekend IIRC and was sporadic enough that I didn't look into it further. I thought it had largely cleared, but now I'm wondering about some ongoing page load pauses..

> ... where DNS props would just fail ... What's a "DNS prop"?

Sorry, I meant probes as in the Chrome errors.