A:Answer If your question is: Can I use my OLD router (that's also a modem) "AS my modem" with my new 8500?
Yes! (Provided your old modem still works with/from your ISP, that is.) Many things have changed though over the past 5 years - and in MY situation in order for our area ISP to increase our speeds to > 80Mb/s, the modems needed to be replaced. So don't stick a very old modem on your network unless your ISP says it'll still work and will still work FAST ENOUGH with any upgrades they may have done.
Mind you, your fastest speed(s) are ALWAYS as fast as your slowest link - so if your "old" router/modem is THAT old, it'll likely _appear_ your new 8500 is slowing down your network when it's actually due to you're using a very old device that (likely) has a processor in it way back when 1.5Mb/s was having a FAST Internet connection!!! (I won't mention my age, but my 1st 1.5Mb/s symmetrical link cost $1250 PER MONTH and was using a modem/switch built for 10Mb/s Ethernet.) Yikes. Hope that helps!