How to build this network design ??

[bokeron2008]

Hello.

I'm a network illiterate trying to create a home network with a design like the one in the image. And when I say Home I mean also cheap. Cisco might be the perfect solution for network connectivity and world peace, but I can't afford it.

http://i37.tinypic.com/33cuiys.jpg

A, B : RouterB is connected to DSL. Both have wifi enabled and are connected to each other by Ethernet.

#1, #2 : Two PCs, #1 connects via wifi and #2 uses Ethernet. #1 can only use DHCP.
#3, #4 : Two PCs, #4 connects via wifi and #3 uses Ethernet.



My main problem is that the Green group must work always.

Group B can go offline at any given time, but #1 must reliably send data to #2 ALWAYS. I can do that just running this Green group isolated from the Red one ... but that means without internet.

The problem comes when I try to make the Green group have internet access : If I have to disable DHCP in routerA to let RouterB manage that and be able to get internet connection ... and the routerB goes suddenly offline ... then #1 and #2 can't connect, and I can't let that happen.

So ... the way I see it, both groups have to work as independent networks except that Green group must acquire internet connection via RouterB somehow. It would be nice if #1, #2, #3 and #4 could share data, but I'm willing to sacrifice that in order to get a reliable #1 to #2 connection.


Well, thats all. That's my question : how do I make it work ?

 

[thiggins]

See if this helps.
How To: One Internet connection - Two Private LANs - SmallNetBuilder

 

[bokeron2008]

Hi thiggins, thanks for your post.


Yes, that helps me clarify some concepts/ideas I wasn't sure about.

In my case ... I would like, if possible, to use what I already have. And that is 2 DSL modem/router that are wifi capable. And a 3rd one, that's also modem/router.
So ... I can only connect them LAN to LAN. THe y have no WAN port, they have DSL (telephone line) port.

Regarding the network structure in the image ... is not set in stone. I just need the functionality on the green zone to remain stable even if the red zone goes offline. I don't mind losing internet when that happens, but having 1 & 2 be able to connect is a must.

So, if that can be achieved with any other network topology, it's fine with me. I just wish it would be possible using what I already have.

What do you think, is there a way ?

 

[thiggins]

What is the purpose of the two zones and why are you using two Internet connections?

 

[bokeron2008]

Hi again thiggins.

I'm not using two internet connections, just one. The oruter that manages that connection is on the red zone.

The purpose for the zones is ... that I have direct control of the green zone and I need to send data from 1 to 2, and I need a reliable connection. And, at the same time, I wish to have internet access.

BUT ... internet access is only available at the red zone, that is not under my direct control, and its router can go offline at any time ... so, I can't let the red zone's router manage the whole network. I need a router for the green zone because that network is vital to me, and then, when the red one is back online, I have internet access.

I can't daisy-chain them because they don't have WAN ports, so I was thinking about having a network with two DHCP servers and setting router A's default gateway pointing to router B.

One of the problems I'm having so far is that, if I switch on the router A before the router B is connected ... then router A's gateway point to his own IP, not the one I set ... only if router B is already online when router A is switched on the default gateway is correctly set.

So ... what could I do ?

 

[thiggins]

Are you trying to isolate clients 1 and 2 from 3 and 4?

If you want 1 and 2 to keep working if Router B's DHCP server goes offline, just convert them to static IP. You should not have two DHCP servers on the same network anyway. Shut off Router B's DHCP server, assign it a static IP address in the same subnet as Router A, but outside its DHCP range. In other words, just convert it to an Access Point.