Can one address have Spectrum internet and ATT internet?

Sure, if AT&T shows your place has fiber available.  Spectrum delivers their Internet via coax and of course AT&T uses completely separate fiber line.

If Spectrum is briefly out of service, how can I switch to our AT&T connection?

@janetj1983 

You have ATT internet with a gateway?

What speed tier subscribed to?

Does the ATT internet work on any device, wired or wireless?

Yes, you can. Ultimately each provider uses a certain type of infrastructure to deliver services to your address. So for example, if you have copper coming from AT&T, any other provider using copper would still use that same copper in the ground - in that case, you may have more copper pairs and they can split it into different services.  The same goes for fiber the best thing you can do is check  what providers service your address. I would start by asking your neighbors, or go to a website like telecom.live to check your address (that’s for Houston, but seems to work for any address) and see what providers and what services are available to your building. To answer your question about Spectrum, Spectrum will use cable which is a completely different  buildout and construction to your address. You’ll basically have ATT fiber (using fiber) and Spectrum (cable) - which are completely different conduits of service- so yes.

"If Spectrum is briefly out of service, how can I switch to our AT&T connection?"

AT&T has a gateway (modem and router combined), Spectrum has a modem and a separate router.  So to switch, your client PCs would just change their network connections to the alternate service, then later change back to the first service.

Yeah, what DaveinCharlotte said, another option is to get an SD-WAN (software defined wide area network) something like a Velo Cloud for example - which will load balance two internet providers in what’s called an “active/active” connection. So if one loses internet, everything instantly fails over to the other network - when the connection is restored - it automatically load balances back.

Another advantage of this, is that the velo cloud out of the box will find the quickest route to whatever path the application or service is requesting to connect to. Example… a YouTube connection might route faster through the ATT connection, while a video game connecting to its game server might connect faster through the Spectrum. The SD-WAN box would prioritize the traffic based on the end point its connecting to.

@my thoughts 

I am going to say the first two question answers are YES.  The last question answer is: I think it will only show up on the wirless laptops and smart devices.  I need the hardwired computers to automatically swap over when Spectrum is down.

@janetj1983, it sounds like you may be having problems on hardwire cutovers and not on WiFi - this is because the IP scheme of the ATT router and Spectrum router are not the same. For example, the “gateway” IP address on the spectrum could be different than ATT. So, your computers (upon the initial hardwire connection) have registered those IP’s, and when you just pull the Ethernet from one router and connect to the other, those same hard wired computers do not update. The solution is to physically reboot the computers, which can be a super hassle. Or just get little WiFi cards that plug into the back of them. The other solution as mentioned above is like a Velo Cloud, which becomes the router in terms of keeping the IP’s the same… and as internet connects and disconnects, it does not change those IP addresses internally to any devices, keeping everything online 100%. 

The SD-WAN is like a subscription service through a telecom provider, but also has some software benefits such as monitoring and prioritizing traffic. If you don’t need all that, just look for a router that has DUAL WAN. There are some small business routers that have that, like little Cisco routers with a WAN1 and WAN2 port. Each port is for a different provider. You would then put your ATT and Spectrum modems in Bridge Mode and let the Cisco do the routing as described in the previous post. Hope that helps!