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I'm setting up two different networks at our office. One is to manage the internet connection, and the other one is to connect to a local server. I believe I should be using a different IP range to achieve this, is this correct? Something like:

Network 1: 192.168.1.0
Network 2: 192.168.2.0

Both network have different routers, and all computers involved have two network cards installed (except for the ones that only need to connect to one of the networks).

I have the following questions:

  • Should I two entirely different IP ranges (192... vs 10...), or can I work with the aforementioned example (which only varies the second-last number group)?
  • Should I use different subnets, and are there specific suggestions regarding this?

I read this question: http://superuser.com/questions/68426/can-i-connect-to-two-networks-simultaneously-with-two-ethernet-cards which does not mention different subnets, but elsewhere I read one should not work on the same subnet when dealing with two networks.

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1  
192.168.1.0 - 192.168.1.255 and 192.168.2.0 - 192.168.2.255 are two entirely different IP ranges. –  David Schwartz Aug 14 '12 at 12:47
    
Some advice: Do not use 192.168.1.x, but use something slightly more obscure. This avoids later conflicts with other networks (e.g. via VPNs or after mergers) –  Hennes Aug 14 '12 at 12:56

3 Answers 3

To be honest, I don't see the reason behind using more than one network interface on each machine. You can just connect each computer to its appropriate subnet and then interconnects these subnets using a router (dedicated router, layer-3 switch, or a Linux box running as router).

For private IP addressing, you can choose whatever ranges you like. The important point is to setup routing correctly.

Using two NICs in machines can be useful in cases like:

  1. Redundancy, high availability, and increased bandwidth for servers (bonding).
  2. Servers requiring access to multiple networks like receiving requests internally and requesting resources from Internet. Even though, this can be done using one NIC.
  3. Running an IP router.
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Yes, having a computer with two NIC's will work fine, but you can only set one default gateway, which will most likely be on the internet side.

Why are you joining every computer to the internet subnet though? A proxy would make much more sense if you just need every computer to access the internet and this could have an address on your LAN.

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You could use 192.168.1.0 and 192.168.2.0 as subnets if you use netmask 255.255.255.0 (/24). If you do that 192.168.1.0/24 and 192.168.2.0/24 will be treated as different networks.

When deciding subnet for local network you should always follow RFC1918 when choosing subnets. It's specified under paragraph 3 Private Address Space.

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