Cannot connect to devices behind TL-ER7206 from ISP Modem WiFi Router

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Cannot connect to devices behind TL-ER7206 from ISP Modem WiFi Router

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Cannot connect to devices behind TL-ER7206 from ISP Modem WiFi Router
Cannot connect to devices behind TL-ER7206 from ISP Modem WiFi Router
2023-06-14 15:56:56 - last edited 2023-06-15 08:58:33
Tags: #TL-ER7206
Model: ER7206 (TL-ER7206)  
Hardware Version: V1
Firmware Version: 1.3.0 Build 20230322 Rel.70951

Good day! I hope everyone is doing well. I would like to ask assistance if this setup of mine still has a chance or would need additional device. My goal is to utilize what I currently have to not spend more on another device if possible.

 

Devices Involved:

-TL-ER7206 Router (DHCP Server Enabled)

-ISP A (Globe) Modem WiFi Router (DHCP Server Enabled, using all default settings provided by ISP)

-ISP B (PLDT) Modem WiFi Router (DHCP Server Enabled, using all default settings provided by ISP)

(No internet or does not work if I make the IP addresses of the 2 ISP Modems the same subnet as the TL-ER7206 Router)

-PC

-Laptop 1

-Laptop 2

 

 

Network Setup:

-ISP 1 and 2 are connected to WAN ports of the TL-ER7206 Router

-PC is connected to LAN port of TL-ER7206 Router

 

-Laptop 1 is connected to ISP A Modem WiFi Router

 

-Laptop 2 is connected to ISP B Modem WiFi Router

 

*From the PC behind the TL-ER7206 Router, I can ping just fine to Laptop 1 and 2 while they are connected on the said ISP Modems. This is a proof that I have a path going to them

 

 

*ISSUE*

Laptop 1 and 2 cannot ping back to PC

It seems something is blocking the connection going IN to the LAN of TL-ER7206 Router

 

*DESIRED OUTCOME*

Able to connect devices wherever they are connected

Either on behind TL-ER7206 Router, ISP A Modem WiFi Router or ISP B Modem WiFi Router

 

 

I hope someone can help me figure this out, what I am missing or if this is not achievable. Open to suggestions.

Thank you and have a good day

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#1
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1 Accepted Solution
Re:Cannot connect to devices behind TL-ER7206 from ISP Modem Router WiFi-Solution
2023-06-14 17:19:41 - last edited 2023-06-15 08:58:33

  @ComPort You need to do some basic reading on NAT (network address translation).

 

It doesn't work because all TPLink routers are NAT devices, meaning all LAN devices hide behind a single WAN IP address (in this case handed out by one of your ISP routers).  You can talk upwards because all TPlink LAN devices appear as if coming from the WAN port of the TPlink but you cannot talk the other way, because there is no mapping from the TPlink WAN IP down to the LAN IP of the target device (you must configure port forwards for each port/service you wish to fix across the NAT function of the 7206).

 

You could make this work by ignoring the WAN ports of the 7206 altogether, defining two LAN subnets on the 7206, disabling DHCP and mapping each to a LAN port which is then connected to either ISPA or ISPB.  The 7206 will take care of traffic routing between the two private subnets thus created.

<< Paying it forward, one juicy problem at a time... >>
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#2
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Re:Cannot connect to devices behind TL-ER7206 from ISP Modem Router WiFi-Solution
2023-06-14 17:19:41 - last edited 2023-06-15 08:58:33

  @ComPort You need to do some basic reading on NAT (network address translation).

 

It doesn't work because all TPLink routers are NAT devices, meaning all LAN devices hide behind a single WAN IP address (in this case handed out by one of your ISP routers).  You can talk upwards because all TPlink LAN devices appear as if coming from the WAN port of the TPlink but you cannot talk the other way, because there is no mapping from the TPlink WAN IP down to the LAN IP of the target device (you must configure port forwards for each port/service you wish to fix across the NAT function of the 7206).

 

You could make this work by ignoring the WAN ports of the 7206 altogether, defining two LAN subnets on the 7206, disabling DHCP and mapping each to a LAN port which is then connected to either ISPA or ISPB.  The 7206 will take care of traffic routing between the two private subnets thus created.

<< Paying it forward, one juicy problem at a time... >>
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#2
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Re:Cannot connect to devices behind TL-ER7206 from ISP Modem Router WiFi
2023-06-14 23:50:27

  @d0ugmac1 Thank you for your reply, will definitely check it out.

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