I'm an IT administrator in school. I use a windows 2003(also have a windows 2008 server ready for testing) file server with 2 NICs. At the moment only one NIC from file server is connected to the Science Labs Network. For simple security purposes the school has 2 separate physical networks: Science Labs and School Administration. For convenience each network has 1 router with same IP address and each router get's internet from different ISP. Rarely when internet goes down on one network I simply switch the cable from the router with no internet to the other, as a result for this down time 2 physical networks become one with the internet from one ISP only and when internet is back on the other ISP I revert the changes. My question is how can I have one file server with 2 NICs connected to these both networks and still keep them separated? I don't need the server to have internet access I just use it for file sharing. To understand my question better here is a diagram of what I wan't to do:

School Network

I still want to keep routers on the same IP because it's convenient for me to switch the cable without changing any other settings on computers. And having two physical networks separate is secure without much of the hassle.

The purpose of this is to schedule on the school administration computers an automatic image backup to a network path on the file server.

  • 2
    I stopped reading after "2003"... Dec 10 '16 at 23:07
  • 1
    Ok, how about on windows server 2008, would that make a difference ? I have a windows server 2008 ready for testing.
    – youdgin
    Dec 10 '16 at 23:11
  • You would need another device that is aware of this new network and the other network, and you would then (for example) 1:1 NAT to, then your server could be and, pfsense for example sysadmin.circularvale.com/firewall/… Dec 10 '16 at 23:30
  • I have a third router wich i can set it on openwrt with dhcp disabled. I will search on internet how to do 1:1 NAT on openwrt and will play with it next week.
    – youdgin
    Dec 11 '16 at 0:18
  • "Ok, how about on windows server 2008, would that make a difference ? I have a windows server 2008 ready for testing." You have an eight-year old server operating system "ready for testing"? I'm sorry but the whole arrangement seems crazy to me. And I'm talking as someone who works in educational IT and is aware that budgets and resources can be an issue. Deploying Windows Server 2008 (or even 2008r2 if that's what you meant to say) on a new server now is a poor decision.
    – Rob Moir
    Dec 29 '16 at 11:21

"For convenience each network has 1 router with same ip address"

this issue is the first of many many inconveniences using the same ip range for both networks will cause you.

The solution is to use non-overlapping IP ranges I.e use for one router and for the other. Give the routers unique ip addresses and use dhcp to automatically make the config changes needed when you move a device from one network to the other. If there are a few machines moving regularly between the 2 networks use static dhcp reservations so you know what IP it's going to get to on each network. There are lots of ways to make it easy to move devices between the networks convenient without giving them the same IP ranges.

  • 3
    +1. Total incompetence = funny results. That is a big bad no, never do that.
    – TomTom
    Dec 11 '16 at 15:00
  • TomTom you mean the quote or the answer ??
    – youdgin
    Dec 12 '16 at 7:24
  • Nath, i hope you do get the networks are physically separated. Your ideea applies when both networks are conected and as I see it for me would be too much of a hastle : 1 Firstly i need to use on like 150 computers static ip addreses (either set on device or on a router through static dhcp) and would best work of course setting static dhcp on both routers but the hastle would come when i need to do the switch from one network to the other when one of the isp is down.
    – youdgin
    Dec 12 '16 at 7:38
  • 2. As a security stand point i don't like where is going: for ex. a student can with his laptop set manually his ip to either of the networks witch is a no go for me.
    – youdgin
    Dec 12 '16 at 7:39
  • I need to use 150 computers static ip addresses (static dhcp or device) because i have scripts set in openwrt to shutdown the internet (and not the network) on one of the labs. Each lab is set on a range of ip's.
    – youdgin
    Dec 12 '16 at 7:47

You have overlapping namespaces. I suppose you could install a NAT device and expose the file server as a different address. To the FS it will belive the source is a different network.

  • You mean a third router, how would i configure that third router say using openwrt conecting the other 2 routers with the same ip. Using vlans?
    – youdgin
    Dec 10 '16 at 23:59
  • Or maybe you mean a third router (openwrt) between the nic2 and the adsl router and somehow configure it's nat to not have overlapping namespaces. Could you elaborate a bit on how would i do that ??? :D
    – youdgin
    Dec 11 '16 at 0:06
  • Setting a 1:1 Nat like Jacob Evans proposed in the question comment section??
    – youdgin
    Dec 11 '16 at 0:21
  • There aren't overlapping namespaces, overlapping networks is the issue.
    – Jim B
    Dec 11 '16 at 20:42
  • The IP addressing is the naming of ethernet addresses, therefore the namespace.
    – Ed Neville
    Dec 24 '16 at 19:20

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