PCs on modem can't find PCs on router

[Brilliant]

Hello, I've had issues with my home network for quite some time.. finally decided to seek for help.

I have a wireless modem on the first floor of my house, where I got cables through the wall running throughout rooms in first floor, ground floor and basement.

I have my small business at the basement, so I have 2 PCs one printer and one external hard disc which also connects directly to a modem/router.

I have 3 PCs from the first and ground floor that connect through the wall to my modem, and everything works well. But for my basement, which only has 1 lan cable output on the wall, I got myself a router so that I can connect all my devices.

I connect the router with my modem, and then the PCs, printer and hard disc on the router. The PCs have internet access, so I know the connection to the modem has nothing wrong to it. But I am not able to access the PCs connected to the router from the PCs connected to the modem, or vice versa.

I was told to not obtain an IP address automatically, so I assigned my modem and router to work on 192.168.10.x and gave my PCs IPs such as 192.168.10.19 Only after setting this up did all my PCs have internet access, but again, no network communication between PCs on modem and PCs on router.

One thing that might be worth mentioning, is that through time, my network keeps going from Home Network: Network, to Network 2, Network 3, and so on... now it's on Network 5. I have no clue why this happens, and if it's related to my problem.

Any suggestions or solutions would be highly appreciated.

[Jay]

You should use a switch I think.

Are you running a cable from the "wireless modem" to the WAN pot on the back of the "router" ?

[kalniel]

The simplest way to use a router to extend a network is to have it act as a simple hub (network extender) rather than a router (network translator). Might just be a case of looking in the manual for how to set it up - typically you'll have an uplink port that you plug the connecting ethernet cable (from the modem) to and then configuring it to act as a network extender. Then it's a case of setting up your homegroup and sharing permissions so the computers can see each other.

[shaithis]

I would simplify it a bit.

Ditch the modem if you can, connect everything to the router.

[directhex]

What exactly is a "wireless modem" in this context? The standard meaning of that doesn't fir the scenario you describe.

[Brilliant]

@Jay
what's a switch? the cable that runs from my modem to the basement goes in the blue port of my router, the wan port.

@kalniel
this sounds like it's exactly what I need... I will have a look at the manual for instructions on how to.

@shaithis
I thought you need to have a modem. My modem is connected to the phone line which receives the internet access, maybe it's more advanced where you are at.. Cyprus is still old school. Or is it possible here too and I just don't know how O.o

@directhex
yes actually it doesn't really matter that my modem is a wireless modem. All PCs connected to it are connected through lan cable, I just said it's wireless cause it is.

[directhex]

@directhex
yes actually it doesn't really matter that my modem is a wireless modem. All PCs connected to it are connected through lan cable, I just said it's wireless cause it is.

And that's what makes no sense. You cannot connect more than one device to a modem.

A modem is a single-connection bridge between a WAN interface (PPPoA, PPPoE, 3G, etc) and an internal interface of some kind (typically ethernet or USB these days). For a modem to be shared between multiple devices, it needs to be connected to a router, which handles the multiplexing tasks. A router can have one or more ethernet connections on it, and one or more wireless networks associated with it. It is common for the modem and router to be the same device for ADSL, and common for them to be separate boxes for cable and VDSL.



VDSL modem with ethernet output on the right; Router with 4-port ethernet switch plus 802.11 wireless on the left.

[Brilliant]

hmm, I didn't know that. I guess the device I considered to be a modem is a router then. It's the device that my ISP provided me with. Does this change the situation anyhow?

[shaithis]

So, 2 routers?

You are going to have to either:

a. Replace 1 router with a switch

b. Disable DHCP, DNS etc on the second router so it essentially becomesa switch/hub.

[directhex]

hmm, I didn't know that. I guess the device I considered to be a modem is a router then. It's the device that my ISP provided me with. Does this change the situation anyhow?

Yes. If you're plugging a router into an already-routed network, you're creating a completely standalone network. Consider this layout:

[internet]--[router]--[pc]
            |      |
            |      |
          [pc]    [pc]

The three PCs in this layout are on a flat network - let's say on the 192.168.1.0/24 subnet.

Now consider the layout you're suggesting:

[internet]--[router]--[pc]
            |      |
            |      |
          [pc]    [router]
                  | 
                  |
                 [pc]

The second router is a device on the 192.168.1.0/24 subnet. That router routes all traffic inside its internal network, and passes it out into the "WAN", where your WAN is actually a LAN. It acts as a firewall. Let's say the second router is configured to use the 10.0.0.0/24 subnet - the PC at the bottom, 10.0.0.1, isn't aware of anything happening up the chain. And vice versa.

If you want a flat network where every device can see every device, then you do NOT want multiple routers - you want to replace the bottom router with a switch, which simply multiplies the number of available ports without doing any kind of routing.

[directhex]

b. Disable DHCP, DNS etc on the second router so it essentially becomesa switch/hub.

As long as he's using the WAN port on the router, that won't work.

It'd probably work as you describe if using only the switch ports in it.

[Larkspeed]

hmm, I didn't know that. I guess the device I considered to be a modem is a router then. It's the device that my ISP provided me with. Does this change the situation anyhow?

No as already stated you are trying to route traffic that is already routed.

An analogy for you.

If you put an amplifier in your car it makes music louder but if you then connect the speaker outputs from that amp to another amp it will only sound like crap because you are amplifying amplified sound and using the equipment in a way it was not intended to be used.

The best solution for what you want to achieve is the ISP supplied router upstairs and a network switch downstairs.

Network switches are very cheap so this is the route I would go.

If your downstairs router has a bridged mode or the ability to possibly turn off the routing features in it then it may act as a switch but not plugged in through the WAN port but for the cost of putting a switch in is not really worth the hassle of configuring it all.

You can buy the switch, pull out the basement router and plug the switch directly in it's place and you are done you should not have to reconfigure anything, provided all machines are on the same workgroup in windows it should just work out of the box.