So the setup is like this:

My main router is an ADSL WiFi router which also has an inbuilt network switch. All switch ports are utilized, connected to various devices via ethernet.

I decided to take a CAT5 to my 3rd floor where the plan was to connect that to a portable router (TP-LINK MR3020) which could be hooked up as and when needed.

Since all ports of the router are used, I got a switch (also TP-LINK TL-SG105). I connected the switch to the 5th port of the ADSL router after removing one device and connected that device's ethernet to the new switch. Works fine.

Now, I took the 100 ft CAT5, connected it to the new switch, took the other end up 3 floors and connected it to the portable router. The portable router isn't getting a DHCP address from the ADSL. (This is a patch cable, not a crossover cable).

If, however, I connect my portable router to the ADSL router directly, it gets a DHCP address assigned.

Any ideas why? The TP-LINK switch is supposed to have auto sensing ports, so in theory it shouldn't matter if I use a patch or a crossover cable.

  • First guess: The 100ft CAT5 cable has a defect somewhere. What happens if you you connect the portable router directly to the ADSL router via the 100ft CAT5 cable? What happens when you connect one of your other devices with the 100ft CAT5 cable instead of the cable it was using before?
    – dirkt
    Nov 15, 2017 at 14:28
  • the 1st question is answered in my post. I get a dhcp assigned by the adsl. I don't think its the cat5.
    – deepakkt
    Nov 15, 2017 at 14:36
  • Ah, you meant "connect my portable router to the ADSL router directly with the 100 ft CAT cable" (could have been some other cable). If the cable is fine, test the switch: Connect it as before to the ADSL router, then remove all other devices from the main router ports and connect those to the switch ports. See if they all get a DHCP address. Test all switch ports that way, in case one port is bad.
    – dirkt
    Nov 15, 2017 at 16:26
  • have you seen this: tp-link.com/us/faq-138.html Nov 16, 2017 at 17:24
  • @batistuta09, thank you! that was the issue, I answered my question below.
    – deepakkt
    Nov 18, 2017 at 9:24

1 Answer 1


Thanks to @batistuta09, the link here gave me the answer. It turns out the adsl and my portable router were operating with the same IP ranges. I changed the IP range my portable router handed out and it fixed the issue.

Solution 3:Change the LAN IP address of the router. Most TP-Link routers use as their default LAN IP address, it may be conflicting with the IP range of your existent ADSL modem/router. If so,the router is not able to communicate with your modem and cause you can’t access the Internet. To resolve the problem, we need to change the LAN IP address of the router to aviod such conflict, for example,

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