Here is what the network looks like:

Network A is 192.168.116.X , subnet 
Network B is 12.32.8.X , subnet

There are no routers present in either of the network schemes. All routing is done through unmanaged switches and hubs. Both networks are peer-to-peer and do not rely on DHCP. All machines have static IPs.

I need any machine on Network B to be able to reach any node on Network A

  • is it desirable for you to assign secondary IPs on the machines in both networks ?
    – Mr.lock
    Nov 14, 2016 at 8:35
  • Yes, that would be ideal but there are no extra NICs and it is not feasible to install a new PCI network interface card in these machines.
    – Eminent
    Nov 14, 2016 at 9:37
  • What operating system are the machines running? Depending on the operating system you may be able to add an alternate address on the same NIC.
    – 3iron
    Nov 14, 2016 at 11:44
  • I think this is a networking problem. There are many ways to solve this. The OP didn't ask how to configure his hosts.
    – Ron Trunk
    Nov 14, 2016 at 15:59
  • What software are the machines running? do they have a default gateway set? if so what is it set to? is purchasing new equipment possible? Is there a server that could be used as a router? Nov 14, 2016 at 17:24

3 Answers 3


You have two layer 3 domains, but no layer three devices. That's a problem.

You can bridge the networks together, but bridging happens at layer 2. It does not change the fact that you have two IP subnets.

I see only three real possibilities, in descending preference.

  1. Buy a router to route between the subnets.
  2. Readdress one or both of the subnets to a common IP subnet.
  3. Configure secondary addresses on both devices for a common subnet.

Maybe other readers have more ideas.

  • +1, but perhaps worth mentioning that a L3 switch can also function as a router?
    – hertitu
    Nov 14, 2016 at 22:53

Add a secondary IP address to each NIC card. The primary being in 192.168.116.X and the secondary being in 12.32.8.X. Or, the other way around - it does not matter which one is secondary as long as each NIC has an address on both subnets.

You do not need a second NIC card. This secondary IP address is added/configured in software.


Since all being static: Proxy ARP

  • Since there are no Cisco devices, I don't see how this is possible.
    – Ron Trunk
    Nov 14, 2016 at 13:57
  • Who's talking about available devices? There's no mention of not adding devices or changes to the networks. Who's talking about Cisco devices? The mere fact that the link refers to a page which explains the Proxy ARP concept doesn't mean that the supplier hosting the page is the only solution provider. Nov 14, 2016 at 14:56
  • 2
    There are no managed devices in the network. If the OP is going to add a new device, then he can simply route without having to use proxy arp.
    – Ron Trunk
    Nov 14, 2016 at 15:34

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