@Let-It-Snowman 

I assume that you are replicating on the Deco the config (PPPoE, etc...) you had on the Asus router.

Is it possible that the modem, in transparency mode, expects the Deco to use the same MAC address as the ASUS router?  If that is the case, you can setup the Deco to use a specific MAC address (on the WAN port), via More / Advanced / MAC Clone.

As a temporary alternative, I suggest seting up the Deco Internet Connection as "Dynamic IP", as if the modem was not in transparency mode.

  @yves_b 

Thank you for your quick reply.  Since you didn't state there is a conflict with me using this Deco BE65 with my older Actiontec c1900a modem, I understand that it should only be a setup issue that I need to figure out to get up and running with it.  We originally tried the Dynamic IP route but that didn't work - can't remember why.  As I mentioned in my first post, there are several user name/password groupings that I'm not sure if I need them or which ones to use throughout this set up process.  The Actiontec modem has its own user name/pw, CenturyLink has its own SSID/Network name/passcode, my Asus Router would ask for my CenturyLink ISP user name/pw - is that the same thing as the PPPoE user name/pw?  

I have a technical enough mind to be dangerous with this set up process and am getting a little confused by all the pieces, acronyms & user names/pw's.  

To answer your question, Yes, my original plan was to unplug the Asus and plug in the Deco - with the same assumption you brought up - replicate the set up the Asus was using for the Deco.  I'm not sure if the modem expects the Deco to use the same MAC address as the router.  I did find where to force a specific MAC address but the set up kept getting hung up at the PPPoE connection process.  About 3/4 of the way though that screen the Deco would turn a solid red.  The app would give me an option to change my user name / pw, but I'd have no idea what user name / pw I should be using and if the ones I were using had changed.  I got stuck with the solid red light and then would reboot the Deco and start over again.  I probably did that a dozen times.  

Side question.  My bonded phone lines come in and are connected to the modem (lower level south end of home).  The modem is in bridging mode.  From the modem, I have the Deco supplied Ethernet cable going to the first node.  My assumption (haven't go this far into the set up process) is that I can then run an Ethernet cable from this node to where my Asus was plugged in (center of our home main level).  From that second node, do I have to run another Ethernet cable to the third node somewhere on the north side of our home or is there a way that the second node can wireless communicate with the third node?

Again - I appreciate any help you or others can provide.  Hopefully my son and I can make some progress on this over the next few days.

Thank you

  @Let-It-Snowman 

Indeed, there are usually several names/passwords involved in such a configuration:

1. administrative (management) names/passwords, required to manage a device or access a site.  Each device/site can have its own.
2. wifi SSID/passwords
3. Internet Connection name/passwords.  That is probably what you mean by "my Asus Router would ask for my CenturyLink ISP user name/pw", and what the Deco expects as "username/password" for the Internet Connection.

Are you sure the Asus router is using PPPoE to connect to the ISP?

Another approach would be to setup the modem in Router mode, and the Deco in Access Point mode.  In that mode, the Deco does not need any ICP username/password.

About your side question: a Deco satellite (third node) can wireless communicate with another Deco, provided the wireless communication is good enough between the two locations.   

It is easier to setup the third Deco close to the second Deco (while it has a perfect wireless connection with it), before moving it to its final location.

If you configure the Deco with an existing wifi SSID/password, you certainly want to disable (or rename) that wifi SSID on the other modem/router, to avoid confusion the client devices.