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I have a Siemens cl-110 (modem/router) in bridge mode connected to the router's (Netgear R7000) WAN port. The router handles PPPoE connection. The modem's ip adress is currently 192.168.1.25 and R7000's is 192.168.1.1.

Internet works just fine, but I can't access the modem's web interface.

If I connect the modem to my computer or to a port in R7000's switch, I can access the modem's web interface. However, when the modem is connected to R7000's WAN port, I can't access the modem's interface because R7000 doesn't root 192.168.1.25 to the modem.

Is there some way to access the web interface, while connected to R7000's WAN port? Can I set-up some static route?

I have already tried changing the modem's IP to 192.168.0.1 so that it is in a different subnet, as other answers proposed, but it didn't help.

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Change your router's LAN IP to a different network, perhaps 192.168.2.0/24, which would change your router to 192.168.2.1, and you should be able to access your modem's web Interface with no issues.

Assuming your router uses the standard subnet mask of 255.255.255.0 (a /24 network), 192.168.1.1 and 192.168.1.25 are considered within the same network (subnet) so the router doesn't have anything to "route" to the modem when you try to access it.

By changing your LAN address to a different network, such as 192.168.2.0, then when you attempt to reach 182.168.1.25 your computer will know it's not in the local network (thanks to the subnet mask) and pass the info to your router at 192.168.2.1 to router (gateway) to handle. The router will look at the destination and decide it needs to pass it to it's default gateway in the WAN side, then the modem should see your trying to reach it's web interface and respond. This a but simplified but should suffice.

BTW, this is literally how I access my cable modem at home and is quite common. However, be aware most ISPs lock down their modems so users can do very little, if any, configuration or changes.

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  • How is this different to what I already tried? I tried setting the modem's IP to 192.168.0.1/24 so that it's in a different subnet to the router's (which has 192.168.1.1/24).
    – Petrakeas
    Commented Dec 23, 2017 at 14:56
  • For this to work relies on one of two things... Either the modem is itself a gateway and is in the same subnet as your WAN IP address (not likely in Bridge Mode), or it is capable of "intercepting" it's own IP address traffic because it knows it needs to (like a Cisco cable modem). If you connect your PC directly to the modem without a router, what IP address do you get and what is assigned by? Modems do not circumvent conventional rules of IP routing in general, so we are missing a piece somewhere if this answer doesn't work.
    – acejavelin
    Commented Dec 23, 2017 at 15:10
  • When connecting the modem directly to the PC, I have to assign an IP manually to the PC so that it is in the same subnet to the modem's IP. For example, if I have the modem to 192.168.1.25, any IP in 192.168.1.x will work for the PC. Also, connecting the modem to the router's switch will work if it's in the same subnet. If I have my router as 192.168.1.1 and the modem as 192.168.0.1 (while connected to the router's WAN port) is it the same as what you're proposing?
    – Petrakeas
    Commented Dec 23, 2017 at 16:31
  • @Petrakeas gotcha... Is your router sophisticated enough to have multiple networks on the WAN port or dual WAN ports? I would bet not, so the likely hood you make this work having internet access and be able to access the modem at the same time is near zero.
    – acejavelin
    Commented Dec 23, 2017 at 17:56
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    The router (R7000) handles PPPoE in my setup, not the modem. I guess the router's WAN port can't be used for regular TCP/IP traffic under this configuration.
    – Petrakeas
    Commented Dec 24, 2017 at 15:28

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