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I set up a modem as a range extender as in this thread. Initially I set it to WDS-only and could connect only via ethernet, so I wanted to login to the modem and change to Hybrid to also connect via wifi. With the default IP of the modem, I go instead to the router page.

Following these methods, I looked at the DHCP table on the router, which does not list the MAC address of the modem. I also tried pinging the broadcast address and then checking the result of arp -a. It returned 5 IP addresses, none with the modem's MAC address. One address timed out, all others gave an error Safari can't open the page.

My machine is connected to the modem and has an IP address that does not show on the router's DHCP table, hence I believe the modem is doing Network Address Translation, as in How to access an adsl modem/router in bridged mode?.

I turned off the router, restarted the modem, got into the router's page, and changed the mode to "hybrid", so now I can connect via wifi. I also set the LAN IP of the modem to 192.168.2.1 to have a different range than the router and left the same netmask (255.255.255.0). I confirmed that I can access this page when the modem is not bridged.

When bridged, the page at 192.168.2.1 does not respond from my machine plugged in to the modem with an ethernet cable or on the modem's wifi.

How can I find the IP address of the bridged modem or access the modem's page when bridged?

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    Your devices must be in the same network and have different IPs. 192.168.1.1 with a 24 bit netmask (addresses from 192.168.1.1 to 192.168.1.254) and 192.168.2.1 with the same netmask (addresses from 192.168.2.1 to 192.168.2.254) are disjoint networks. – Piotr P. Karwasz Jan 1 at 21:57
  • You are right. I changed the IP to 192.168.1.2 and now I can see the router's page. I can now also see my machine on the ARP Cache Table, I don't know why it wasn't showing before. Can you write an answer? – miguelmorin Jan 1 at 23:04
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You had an IP conflict: both routers had the same IP. After you changed your modem's IP, you placed it in another network: a netmask of 255.255.255.0 indicates that all devices in the network have the first 3 numbers (or 24 bits) of the address equal. The ARP tables won't detect it, since they have only one entry per IP. You must change the IP of your modem to something like 192.168.1.2.

A solution that can help in the future: choose a random number <n> between 2 and 255 and setup all your devices to use different addresses in the network 192.168.<n>.0/24 (addresses of the form 192.168.<n>.*). Embedded devices have a default IP address of 192.168.0.1 or 192.168.1.1, so you'll always be able to join them, by adding a second IP address to your computer's network interface (just to change the device's IP).

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