Can you go back and read my question on structured wiring. If you have that in your home you will be able to get rid of the Range Extender and park the modem and router anywhere in the home, and get better service out of the whole system.
Can you tell me where you have the various pieces of equipment installed?
Typically, the better arrangement to use is to place the modem in bridge mode. Then connect the router to the modem and run the router in full router mode. That connection can be through an ethernet cable or through the wireline adapter. Both should work, but an ethernet run, as is within a structured wiring bundle would be the better solution.
The switch would then be connected to the router.
The VOIP adapter would then be connected to the router as the router would be easier to set for port forwarding if required, and you would probably have control over the ALG SIP setting which can interfere with Voip equipment. It could also run through the switch, depending on the network layout in the home.
Here is a post on Structure Wiring. Msg #23 of 23.
If you come back and indicate that you're in an older home without structured wiring, then, ok, we'll have to figure out how to place everything so that the network does what you need it to do.
All you do is connect the switch to the router via ethernet. The modem should take care of any LAN IP address for anything that connects to the switch.
When you run a router like the DIR-655, you should assign an IP address to it that is outside of the modem's IP address range. That way, you have the ability to log into either the modem, or the DIR-655 if any changes are necessary. The DIR-655 should pick up an IP address from the modem, but if I was going to allow the modem to set the address for the 655, I would probably use a static address, assigned within the modem so that I knew what it was going to be. Newer routers have an access point mode that does all of this for you, just a matter of selecting it.
There are a couple of ways to do this:
1. Bridge the modem
2. Connect the router to the modem via ethernet or via wireline. I would run a reset of the router here and set all the parameters.
3. Connect the switch to the router
4. Connect any other devices to the switch or router.
1. With the 655 disconnected from the modem, power it up.
2. Log in and turn off the DHCP and assign an IP address that is outside of the modems IP range
3. Save the settings and reboot the router
4. During the reboot, connect the router to the modem via ethernet or Range Extender
5. After the router is finished rebooting, connect the TP-Link Switch and power it up. Anything connecting via the switch will pick up its IP address from the modem.
6. Connect any other devices to the switch or router.
The Range Extender should be invisible to the modem or router. For best results, you should try to place both ends of the extender in rooms that are on the same side of the circuit breaker panel. So, if the basement socket is on a circuit breaker on the right side of the panel for example, have a look at the panel list and choose a room upstairs that is on that same right hand side. Place the other end of the extender in that room.
That might be true if the modem is running in Bridge mode. I don't know if there is only one active port on the 3825 when its bridged, but its possible. If its running in Gateway mode, it won't matter which modem port that the router is plugged in to. And.....when you connect the switch, it won't matter which port you use on the router.