Networking – Accessing a bridged DSL modem from behind a Linksys router

modemnetworkingrouterrouting

I’ve got a pretty standard home network setup that looks like this, starting from the ISP:

  • An ISP-provided DSL modem (ActionTec PK5001A if it matters), IP address 192.168.1.1. I followed these instructions to put it in bridge mode.
  • A Linksys WRT54GL router, IP address 192.168.1.2. It's connected to the modem through its WAN port and the PC through a LAN port.
  • My PC, IP address 192.168.1.95.

Almost everything is working hunky-dory: I can access the Internet just fine. There is just one piece that’s inconvenient, which is that I can’t access the modem from my PC unless I unplug my PC from the router and plug it directly into the modem.

I’m guessing this is because, being a LAN address, the router tries to route it internally; in particular, the router’s routing table looks like this:

Destination       Subnet mask       Gateway           Interface
207.225. 84. 51   255.255.255.255     0.  0.  0.  0   WAN
192.168.  1.  0   255.255.255.  0     0.  0.  0.  0   LAN & Wireless
  0.  0.  0.  0     0.  0.  0.  0   207.225. 84. 51   WAN

I thought I might be able to fix this by adding a route for destination 192.168.1.1, subnet 255.255.255.255 (I only want to change the route for exactly this IP), gateway 0.0.0.0 on the WAN interface. However, when I try to add that route, the router pops up an error message saying only “Invalid static route!.”

Why is this route invalid? How can I access my modem from my PC without shifting my Ethernet cable from the router to the modem?

There is an existing question that seems quite similar; however, it was marked as a duplicate of a question that no longer appears to exist, so there is no longer an answer to that question.

Best Answer

By far the simplest solution is to move your modem or your LAN to a different subnet.

Eg:

  • Modem: 192.168.1.1
  • Router: 192.168.2.1

Then it wont have the modem as part of the DHCP pool and will treat it as a remote network (all remote networks go via the same port withe a “router on a stick”).

It’s not uncommon for modems to change over to 192.168.100.1 or similar when bridging for this very reason.

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