My internet comes in through a D-Link DIR-655 AP/router which has four ports. Not enough, so downstream from the 655 is a Trendnet TEG-SBOg gigabit switch. One of the 8 switch ports is connected by ethernet to the other end of the house, where I have just plugged in a D-Link DL-624 wifi AP/router.

It is receiving communication from the DIR-655 router and I can access the internet over wifi there (it is a strong wifi signal and should be up to 13 Mbps over the internet, but it is slow. However the slowness seems to have started before I hooked up the AP there, in fact just after the last android upgrade, so maybe nothing to do with the signal.)

My android phone tells me that the IP# of the 624 AP is 192.168.0.103, but I am unable to access that address in my firefox browser on my Ubuntu linux desktop. So I used the phone to log onto the wifi of the 655 near my desktop, and it is also showing 192.168.0.103.

So I am not understanding something fundamental here. They cannot both be .103, and if either were, I should be able to reach the admin panel at .103 and log in.

BTW, my internet comes to my house over fiber optic and there is a gateway (is this the right term?) outside my house where the optical is converted to copper digital. Could this be the 192.168.0.103, or is it something else? (it is not the 655 which is at 192.168.0.1

The 655 router is probably acting as a DHCP server too? It's LAN IP address will correspond to the gateway assigned with devices connecting to it. I'm guessing that the 624 is probably acting as a bridge, so just passing IP traffic through devices connected to it. If you log in in to the 655 router web interface (reached via 192.168.0.1), you'll generally find that it can show an ARP page listing the MAC addresses of connected devices, and their IP address assignments. It's likely that the 624 is still at default settings. You're better to configure it offline from the rest of the network, and give it a unique IP address for the LAN subnet. (It has an in-built DHCP server too, but you're best to leave the first router to do that job IMHO.)

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I wanted to reply to this last night (while the forum is more active), and while Ferrari's comments moved me forward, they also raised a host of questions in my mind, which continuous googling last night and this morning have served only to increase my confusion. With apologies, we are dealing with A--C's at my end. Let me summarize where I am:

DHCP shows to be turned on in the 655's admin panel.

I had previously reset the 624 to factory settings, intending to deal with passwords but was unable to reach it over the lan. So you are saying that I should just connect it directly to a computer with an ethernet cable and it does not need to be connected to the internet?

Assuming that I understood that correctly, in order to "give it a unique IP address for the LAN subnet", I have been looking in the admin panel of the 655 trying to figure out how to do that in the 624 (assuming they are either the same or approximately so).

In the WAN section under "Status/Device Info" it shows the Connection Type to be: DHCP Client. Assuming that I would be doing this in the 624 admin panel, I would be changing this to "Fixed IP#", yes?

If so, to do this, I would go to "Setup/Network Settings" and untick "Enable DHCP Server", yes? and if so is there anything else I need to do to complete this objective?

Or do I assign the 624 a unique IP # in the 655 admin panel? If so, I have no idea where to start on this.

And, while I am thinking about it, do you recommend turning UP&P off in all my routers (I understand this is a weakness if the router is ever attacked.)

Thanks for any further assistance (from anyone.)

Not enough information since we do not know the exact configuration of either router nor how the 624 is wired into the 655. However, since you reset the 624 it is reasonable that they both have the same LAN address and DHCP configuration. If you wired the 624 to the 655 using the WAN port then the networks are separated because of the router functionality so one device having the same IP address is possible but there isn't a conflict. If the 655 is plugged into the 624 via a LAN switch port then both have the same LAN IP address and DHCP settings so there will be conflicts and you would be having problems.

If you plug the 624 into the 655 via a LAN port you would need to change the 624s LAN IP address as well as disable its DHCP server. So basically you have an AP and 3 port switch. Any wireless device will authenticate via the 624 and acquire an IP address from the 655. If you plug into the WAN port and reconfigure the 624 in bridge mode (depends on firmware) it behaves the same way. You still need to configure the device disconnected from the 655 is best via a wired port.

From the sound of it, you have a double-NAT setup, but both NATs are using the same subnet, which can cause all kinds of confusion.

The 655 router is acting as a DHCP server with a 192.168.0.x subnet (we'll call this the "primary" subnet).
The 624 router is plugged into the 655 and has its own address on the primary subnet, but is also acting as a DHCP server, also with its OWN 192.168.0.x subnet (we'll call this the "secondary" subnet).

So your phone has a 192.168.0.x address on either subnet, but they're not the same, which is why when it's on the 624 network your desktop on the 655 network can't access it (your desktop doesn't know that it needs to connect to the 624's IP address, and then push its way to your phone.

Please confirm if this is the case. The easiest way would be to log into the admin panel for both routers, and see how the LAN is configured. Do they both have DHCP servers enabled with 192.168.0.x for the address?

If so this is easy to fix, but I want to confirm this is the setup first before changing things.

Also, you didn't mention it, but when you connected your phone to the 655 wifi, was your desktop then able to connect to it?

Apparently my OP was not clear.

655 is connected to the internet via its WAN port
one of the four lan ports of the 655 feed a gigabit switch
one of the 8 lan ports of the switch feed the 624 so the 624 is at the "end of the line"

With this clarification, let us concentrate on this to minimize the contingencies:

What information will be helpful with respect to the "exact configuration of (each) router"?

Yours causes me to remember that I was unable to connect to the internet wirelessly through the 624 when it was connected via its wan port, only when connected to one of its lan ports. Does this reveal anything?

And my questions remain on how to turn off DHCP (see above)

Thanks

Yes - most routers can operate in "router mode" or "bridge"/"access point" mode. In order to switch from router mode to bridge/ap mode, you connect the upstream connection to a LAN port instead of the WAN port and disable the DHCP server.

You likely were having issues because both routers were trying to create the same subnet. Had you changed the 624 to use a different subnet it probably would have worked fine, but you would have had a double NAT. Instead you inadvertently switched the 624 to bridge/ap mode, which means the 655 is now the only one controlling the network, and the 624 is just acting as a wired/wireless bridge. You should have disabled the 624's DHCP server in the process, do you remember if you did?

Thanks for that very helpful information.

I have raised questions above as to how to disable the 624's DHCP server. Is what I have outlined above correct?

Also will the 624 have an IP#, and if so, how do I reach it from my desktop which is hardwired to the 655? The original post was about how to find it's IP#.

If not possible, do I instead need to disconnect it from where it is being used, bring it here to my desktop, and connect via ethernet cable?

If the 624 is operating in bridge mode, it should have been assigned a DHCP IP by the 655, or you would have manually set a static IP. If it's DHCP, you could check the 655's DHCP client list to see if you can find it. Once you find it, you would just go to that IP with a web browser like you would the 655's internal IP. Once you're on its config page, it should have an option to disable the DHCP server. It's been a long time since I've used a D-Link router, but it SHOULD be pretty straight forward, usually just a check box.

I looked through the online manual and the 624 does not appear to have a bridge mode.

So first thing is to disconnect it from the 655.
Connect a cable from your PC to a LAN port of the 624. The PC will get a DHCP address from 624 if powered on.

Using your web browser enter 192.168.0.1. The default username is admin, and leave the password blank.

Once logged in click on the advanced and LAN tabs. You should now be able to turn off the DHCP server. You need to set an address that is outside the range of the 655 DHCP server. You need to log in to the 655 and check its settings.

In the WAN tab you can set up the wireless settings as desired, SSID, password etc.

Save the settings.

Now plug the 624 into the 655 using a LAN port. Anything that connects via the 624 will acquire a DHCP address from the 655. Wireless devices will use the SSID and password you set above and will get an IP address from the 655.

Both: Great Stuff!

I think I have what I need to get this sorted, but would also like to know if you recommend turning off UP&P to make it more secure, or not as the case may be?

I would disable UPnP

I realize that this is rudimentary, and it is embarrassing to admit it, but I don't seem to be able to reach the admin panel of my router.

I have brought the 624 to my computer, plugged one end of an ethernet cable into the 624 wan port and the other into the ethernet port of my computer. Ifconfig shows eth0 ip# to be 192.168.0.100, but when I put that IP# into my browser, it returns this:

"This webpage not available"

How do I get into the admin panel of the 624?

Thanks

Two things:
1) Why did you plug your computer into the 624's WAN port? That won't accomplish anything. You would need to plug it into a LAN port, and the 624 would need to have its DHCP server enabled for it to work.

2) That's your computer's IP, not the router's IP.

Many thanks. The simple answer is that I didn't know any better (having read, but apparently not understood Michaelk's from a few days ago, but the passage of time worked against me), but thanks for pounded it in. Have now plugged the cable into the lan port and deducing from the IPaddress of the computer, assumed that the router would be at 192.168.0.1. It is! Yippee. Progress.

The DHCP page shows that DHCP is enabled, so I changed it to disabled. Below that on the page are some choices relative to fixed IP. I assume that I should choose fixed, but unsure what final octet to enter. The DHCP IP Address Range of the 655 is shown to be 192.168.0.100 to 192.168.0.199. Do I understand that it should be any number outside that range (obviously not 192.168.0.1) but do I need to take care that there is nothing else on the lan that has that number already?

Do I need to fill in the mac address?