Three boxes running three different ubuntu flavours (14.04, 14.10, 15.04). I'm trying to get all of these to talk between themselves, while being on different subnets, and I can't figure how, yet.

Problem is that my ISP provides a router for the TV, phone and internet. We cannot change the hub's lan range (, while my lan with my own router is on (and I don't want to change it).

Here's the setup: enter image description here

My ISP's hub/router is on, so that's the gw facing internet. My own router is connected (DHCP) to this router, its LAN address is thus in .

I have PC1, PC2 and PC3 in, going on the Net thru my own router, which is connected onto my ISP-provided router in Those PCs can connect onto my

Now, I have to connect a PC directly onto my ISP-provided router; it'll have a address, and cannot see other devices into . I'm not that well-versed in routing, I'm wondering what can I do to get it to see PCs onto ?

Oh, and the easy way is out : I cannot add a static route on (the ISP gateway).

Any ideas?


  • I always modify my ISP's router internal IP to suit my needs so I've never attempted this with the restrictions you state. I'll be watching this for answers though.... – Elder Geek Apr 20 '15 at 15:21
  • You might find this interessting: linuxquestions.org/questions/linux-networking-3/… post 11 may provide some clues – Elder Geek Apr 20 '15 at 15:25
  • Elder Geek : that's what I'd done, but my ISP's router is quite dumb (or assuming most of its users are !). Not much I can change on it. First thing I'd have done would be to switch its LAN config to suit my own on, or add a static route on its config, but no, I can't. – J.F.Gratton Apr 20 '15 at 15:48
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    Disable firewall and NAT on your router, then create a static route in the PC on network pointing to your router's WAN: route add -net gw 192.168.2.X – Eric Carvalho Apr 20 '15 at 16:01
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    Accordingly to your diagram, you should add the route to PC#3 (the one with IP address route add -net gw – Eric Carvalho Apr 20 '15 at 18:57

You should add the route to PC#3 (the one with IP address

route add -net gw

Or you can edit your network connection to automatically include a static route when the connection is established (IPv4 Settings tab -> Routes button):

enter image description here

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