Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I have two TP Link routers, one is connected to the ISP and the other's WAN is connected to one of my Ethernet Ports (assigned IP from router1 192.168.1.200). Hosts in the 2nd router (192.168.0.0/24) can ping hosts on the 1st router but vice not versa).

Hint: I added a static route from router1 to network 192.168.0.0/24

share|improve this question
2  
So, what is your question? (And why are you connecting a router's WAN port to a local machine?) –  slhck Jul 30 '13 at 11:36
add comment

1 Answer

up vote 5 down vote accepted

Both your routers are performing Network Address Translation on traffic going from their LAN interfaces to their WAN interface. If you disable NAT on the second router, your problem will most likely be solved. If the option is not included in the manufacturer's firmware, you might want to check if your devices are compatible with DD-WRT.

Here's what happens when a Device 2 connected behind Router 2 pings a Device 1 behind Router 1:

  1. Device 2 issues an ICMP echo request to the destination of Device 1. Since it doesn't know any specific route to 192.168.1.0/24, it sends it to its default gateway: router 2.
  2. Router 2 receives the packet from Device 2. It performs Network Address Translation (Port Translation), so that the packet sent to Device 1 seems to come from the router itself, on a randomly selected port. For instance, the packet will seem to come from Router 2, port 12345.
  3. Device 1 will receive the packet from Router 2 and see that the source IP is Router 2's, and the source port is 12345. It will then answer the request.
  4. Router 2 receives the answer and knows that everything going on port 12345 should be sent to Device 2 since it has an entry in its translation table.

Topology

EDIT: If you simply want to extend a network, you might want to consider giving Router 2 a static IP address in the same subnet as Router 1 (for instance: 192.168.1.253), and connecting a LAN port on Router 2 to a LAN port on Router 1. You would simply not use the WAN port on Router 2.

share|improve this answer
    
I'll try it sir and will get back to you. Thanks a lot for your professional response. –  0xab3d Jul 30 '13 at 18:28
    
Sir, I was unable to set a static ip for the ethernet port, sorry for the bothering, I really want to learn, but I don't have the expertise, so can you detail more, from which router should i assign the static ip, can you write the whole scenario? Thanks a lot in advance. –  0xab3d Jul 30 '13 at 22:02
    
Basically, you would open up the Web interface of Router 2 and assign it a static IP address (for instance: 192.168.1.253) on its LAN interface. I don't know how to do that on your particular router model, but this is a tutorial on how to do it on one of the TP-Link models. Once you set that, you hook a cable from one of the LAN ports on Router 1 to another LAN port on Router 2. Your networks will then be bridged together. Do not use the WAN port on Router 2 in that setup. –  Gregory A. Lussier Jul 31 '13 at 12:08
    
Aha I see, then all other devices on Router2 will be assigned by Router1's DHCP server, no?! –  0xab3d Jul 31 '13 at 23:47
1  
Yes, indeed. You've got a point though: you should only enable one of both DHCP servers in that case. –  Gregory A. Lussier Aug 2 '13 at 3:39
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.