Hello, I have a 4 computer MS LAN connected to a router that is connected to a ISP disk outside the house and all computers have internet access. I now want a redundant backup on connecting to the Internet. I have a Wild Blue Internet Disk outside the house that we used to use. Can I install another LAN card and just have that connected to Wild Blue?
Yes, you can have a second network connection. As long as it uses a different local network, it won't be a problem. So for example, if your primary router is using the 192.168.1.x network, the other one has to be different, say, 192.168.2.x.
However, you can only have ONE default gateway. And if each internet connection claims itself as the default gateway (which it surely will), only ONE will be used for internet access, the other will be IGNORED. Which one is used just depends on which gateway has the lower metric (part of the TCP/IP configuration for the client).
That's why this is sort of a trick question & answer. Yeah, you can technically do it, you can have multiple internet connections per se, but for all practical purposes, it's useless. The only way to effectively leverage multiple internet connections is to use a multi-WAN router, which can balance the load across all its internet connections, or even provide a failover connection, on behalf of all clients of that router.