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User1
Asked: 2011-04-19 18:39:55 +0800 CST

Connecting two computer on different sub-nets

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I have a site with wireless (192.168.0.0) and a wired network (192.168.1.0). Each network has its own DHCP server and other such infrastucture. There is an Ubuntu Linux machine that has a connection to both networks. Can I somehow configure this Linux machine to allow two computers on these separate networks to communicate?

I heard that bridges do not work with wireless hosts. I think I want a NAT but most documentation I have found tries to connect some isolated network to the Internet. I do not need that in this case. I just need one computer from 192.168.0.0 to transfer files to a computer in 192.168.1.0. The must be some simple answer.

linux ubuntu networking nat bridge

3 Answers

  1. There's no need for NAT - all you should need is for the hosts needing to contact each other to have a route via the Ubuntu machine (its IP on the same network as them, of course):

    route add -net 192.168.0.0/24 gw ubuntulinux.on.net.0.0 # run this on the host on the wired network for it to reach the wireless network
route add -net 192.168.1.0/24 gw ubuntulinux.on.net.1.0 # run this on the host on the wireless network for to reach the wired network

    and IP forwarding activated on the server:

    sysctl -w net.ipv4.ip_forward=1

    Also, check the server isn't filtering traffic: iptables -nvL FORWARD should come back empty. No routes should be needed on the server if the interfaces are configured correctly.

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  2. Brigding won't work for different subnets, what you need here is routing.

    I'm not familiar about how Linux does routing sorry so all I can provide is this link.

    https://help.Ubuntu.com/community/Router

    its not much but if you read it you should be able to grasp the basics of routing.

    If you had a Cisco 2800 router I could help you further.

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  3. You just need basic routing.

    Make sure you have the following line in /etc/sysctl.conf:

    net.ipv4.ip_forward = 1

    Then, for hosts on 192.168.0.0/24 make the Linux box IP address their default router (its 192.168.0.x address). Then on the hosts on 192.168.1.0/24 make the other Linux interface the hosts default router. Then they should be able to communicate by giving IP addresses. mapping to names is another matter, most easily done by editing /etc/hosts files on the other hosts.

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