Modem and Router (OpenWrt) gateway have the same IP. Can't access LuCI wirelessly

satrapes · October 29, 2020, 9:50pm

Hi,

I just bought a Linksys EA6350v3 router in order to experiment with networks and OpenWrt in particular.

My modem/router was provided by my ISP (Technicolor DWA0120) and the gateway has a local IP 192.168.1.1 which is the same as the default gateway OpenWrt address on the new Linksys router. I have connected the router to the modem/router with a LAN cable.

I (think I) have turned off wireless in the Technicolor modem/router and have only enabled wireless on the Linksys router. The problem is that this is a very poor device and I haven't found a manual anywhere.

I can access LuCI when I connect my laptop with a LAN cable to the router but not if I connect wirelessly. When I type 192.168.1.1 I will go to the modem's admin page.

I have noticed that all the devices that are connected to the router (Linksys) appear as connected by Ethernet to the modem/router according to the modem/router's admin page

How to solve this? Do I have to change the gateway address of OpenWrt router?

P.S. Forgot to say that I am just getting started with OpenWrt so just using mostly default settings.

Cheers,

Sat

peternikolow · October 29, 2020, 10:42pm

Easiest is to unplug now modem and router to see router only.

Then you need to reconfigure router to be like a "dumbAP" and to act as AccessPoint.

Because running router after modem went you into different set of issues like double-NAT.

Here is how to do it:

Meanwhile set AP (ex-router) with fixed IP like 192.168.1.2

satrapes · October 30, 2020, 11:00am

Hi,

Thanks for your reply. I updated my post to make it clearer.

I don't think there is a setting to change the default gateway on the modem/router. Unfortunately I haven't found a manual for it anywhere.

I had already seen this page but thanks for pointing it out, I now understand that I want to use Linksys/OpenWrt as the router and Technicolor as just a pass-through. My modem/router supports DMZ so I am trying to decide between using modem/router as a router with DMZ towards the Linksys or just in bridge mode. Or even in IP6.

Cheers,

Sat

peternikolow · October 30, 2020, 11:15am

Linksys router have a settings to setup it's own IP that can be accessed from LAN.

satrapes · November 4, 2020, 12:55am

Update:

My (desired) setup in the future will look like the photo :

For now I only have a subset of it.

To add a few words to the pic, I have setup my ISP Modem/Router to
a) have a different subnet to the OpenWrt one (192.168.2.0/24 to 192.168.1.0/24 for OpenWrt)
b) set a static IP for the OpenWrt router (192.168.2.2) and
c) to add OpenWrt in a DMZ.

Therefore as far as I understand there is no Double NAT issue.

On the OpenWrt I have followed the instructions here here and here to setup the local IP of OpenWrt LAN statically to 192.168.1.1 and the IP of WAN statically to 192.168.2.2

For the time being my problem is the following.
I don't know how to setup OpenWrt so that the devices on the DMZ LAN get an IP address from a DHCP server running on OpenWrt and I can't access the LuCI web interface wirelessly.

I can connect wirelessly to OpenWrt device and to the ISP Modem/Router and browse the internet without a problem, however I have noticed that when I check the list of IPv4 devices on the ISP Modem/Router web interface they all seem to get 192.168.2.x type of addresses and I can't connect to 192.168.1.1 OpenWrt LuCI web interface.
When I use an Ethernet cable to connect my laptop to the OpenWrt router I can access the web interface and my laptop seems to get a 192.168.1.x address from the DHCP server.

Do I need to change any other settings?
Am I right to think that if I get an address in 192.168.1.x I should be able to reach OpenWrt when connected wirelessly?
I have toyed with the DHCP settings unsuccessfully, do I have to restart both router devices for changes to take effect?

P.S. Dotted lines are meant to represent wireless connection while solid ones mean a wired one.

mk24 · November 4, 2020, 3:02pm

Usually a home network would have all the LAN devices in one network, the one after the OpenWrt router. Treat the ISP modem/router as only a connection to the Internet. The only thing in its LAN would be the WAN interface of the OpenWrt router. The ISP modem / router wifi should be turned off, and any extra Ethernet ports on it left unused.

The DMZ feature concerns incoming connections only. If like most home networks you don't run any servers and therefore don't have a need to be exposed to everyone on the Internet, leave the DMZ off.

satrapes · November 4, 2020, 3:13pm

Thanks mk24. In your case does mean also disabling the DHCP on the modem/router and only enabling one on the OpenWrt router? In all fairness I should have probably tried already the simple case before trying the more complex one.

The reason I decided to do this though is to learn more and from a naive perspective, I would have thought that it would be possible to specify the location of the DHCP server.

I will try the following to see if I can get 192.168.1.x addresses wirelessly:

Keep the same setup and mess with the DHCP settings on the OpenWrt router but restart the devices after making the changes. Should/(How would) I clear any cached DHCP addresses on windows and on Linux?
Disable wireless and DHCP on modem/router and enable DHCP on the WAN interface of OpenWrt only.

mk24 · November 4, 2020, 3:18pm

The modem DHCP can stay enabled but it would only assign an IP to the OpenWrt router since that is the only device in the modem/router's LAN. The OpenWrt DHCP server would issue IPs to LAN devices.

To cause an endpoint device to obtain a new DHCP address it is only necessary to disconnect / reconnect from the LAN either by turning wifi off and back on, or unplugging the Ethernet cable. Leave the cable unplugged for about a minute if wired.

satrapes · November 4, 2020, 3:21pm

Ok this is a bit puzzling to me now because my current problem is that from the modem/router device list when both DHCP servers are enabled the devices in the LAN of OpenWrt get addresses from the modem/router. I don't see how that would change if I don't change any setting on OpenWrt or I don't disable the DHCP on the modem/router.

mk24 · November 4, 2020, 4:02pm

Connect the OpenWrt WAN port, not a LAN port, to the modem/router. With a default configuration in OpenWrt and no IP conflict, it should work.

Default configuration is for WAN to be a DHCP client, so it should obtain a 192.168.2.X IP from the modem router, which will be shown as Upstream IPV4 on the OpenWrt main status page. Devices in the LAN will obtain a 192.168.1.X IP from OpenWrt.

satrapes · November 4, 2020, 4:14pm

Thanks again, I just checked and I have correctly connected the OpenWrt WAN port to a LAN port on the modem/router.

Also according to these instructions I have set WAN port of OpenWrt to be a static IP address which is the same as the one that I have statically assigned for it on the modem/router LAN.

I found the issue, basically I was confused about which wireless phy to use and I accidentally used the 5GHz one which was disabled. All good now.

P.S. I do have a question though, if you wanted to connect wirelessly the OpenWrt router to the modem/router would you have to use the 2.4GHz antenna for connecting the OpenWrt WAN to the modem/router LAN and the 5GHz one for your OpenWrt LAN (or vice versa)?

system · November 14, 2020, 4:14pm

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