I would like to preface my question, by saying that I know my way around consumer grade networking gear, but I am a complete beginner at enterprise grade network gear. The setup that I am planning on doing is a failover configuration with two different internet connections. The primary will be a gigabit fiber connection (AT&T fiber), and the secondary connection will be a much slower coax connection (Comcast Xfinity). My issue is that if I use the AT&T fiber connection, as my primary connection. Xfinity TV's online streaming service does not recognize that I am on my home network; therefore, I am only able to access a fraction of the content on the service. Is there a way, in a failover setup, to automatically route all outbound network traffic, whose destination is Comcast's URL, to the secondary connection?

Yes, it is possible to
a. have a primary and secondary wan connections.
For example I have bell 1gig and cable 100/20 backup service
My email accounts all go to the secondary.

b. Yes it is very possible to segment outbound traffic to go out a specific wan.

I have successfully setup the dual WAN connections, but I am having trouble setting up the routing/firewall rules to get Xfinity Stream to detect that I am on my local network. The problem that I am having is that Xfinity seems to be using large variations in possible IP address for their platform, and I am only seeing ways to route traffic via IP addresses. As opposed to using the Xfinity stream URL.

Unfortunately I have no ideas what infinity stream is, diagrams and your config would help.

/export hide-sensitive file=anynameyouwish

I was able to figure out how Comcast(ISP) was doing the "in-home" network check. They are downloading and running a json file from a server, in order to see if your internet connection was using their network. I was successfully able to block the server from using my WAN1(AT&T(ISP)) connection, by using a mangle rule marking the connection using that server's IP address. Then I used two firewall filter rules, the first firewall rule accepts the connection if the in or out interface is WAN2(Comcast(ISP)), and the second firewall filter rejects the connection if the in or out interface is WAN1(AT&T(ISP)). The problem with this is that the servers sending the json file could have a large range of different IP addresses. Is there a better way to do this, or to automate the IP address detection?