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I have a router/gateway with multiple NIC's set-up for multiple LAN's. I have provided a brief description of the layout below.

LAN1
192.168.15.1
255.255.255.0

I use LAN1 for the local network, no restrictions just a simple LAN for all my home devices.

LAN2
10.15.0.1
255.255.255.240

LAN2 Used for internet facing services E.g game servers

I have an Ubuntu 14 server also with multiple NIC's and this is where the problem starts

NIC1 connected to LAN1 Static config

192.168.15.254
255.255.255.0

NIC2 connected to LAN2 Static config 

10.15.0.2
255.255.255.240

My interface config

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto p2p4
iface p2p4 inet static
        address 10.15.0.2
        netmask 255.255.255.240
        network 10.15.0.0
        broadcast 10.15.0.15
        gateway 10.15.0.1

#HOME.LAN
auto p2p3
iface p2p3 inet static
        address 192.168.15.254
        netmask 255.255.255.0
        network 192.168.15.0
        broadcast 192.168.15.225

The systems routing table

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.15.0.1       0.0.0.0         UG    0      0        0 p2p4
10.15.0.0       0.0.0.0         255.255.255.240 U     0      0        0 p2p4
192.168.15.0    0.0.0.0         255.255.255.0   U     0      0        0 p2p3
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0

If I have just one NIC configured say NIC2 I am able to ping it using my windows machine connected to LAN1 and am able to access the services on it say game servers.

If I enable both NIC's on the Ubuntu server I can no longer ping NIC2 but I can ping NIC1 from the windows system.

This also works the other way around as in if just LAN1 is connected it can be accessed from a client on LAN2 & LAN1 but not when both NIC's are active.

When I connect my Ubuntu laptop to LAN2 the same is true for that network. I can ping NIC2 but not NIC1, and If just NIC1 is connected I can ping NIC1.

Then I connected my laptop to both networks and this showed the same result. Windows machine could only ping the laptops connection to LAN1 and the Ubuntu machine which at this time only had NIC2 configured could only ping the laptop on its LAN2 connection.

When both NIC's are configured on the Ubuntu server I can no longer access its services via LAN2, however they are still available to the internet and systems connected to LAN2 only.

I think this might be a routing issue and have found lots of info regarding setting route too and from certain networks, and default NIC's said it is network traffic. I have tried many solution and none have made any change to the behavior of my network.

I also have a NAS connected to these networks via it's two NIC's and this can be pinged by any client on any LAN.

If any one could point me in the right direction, or shed some lights on this I'd be grateful.

sugab
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Duncan Rix
  • 1

1 Answers1

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You did not mention enabling ip_forward anywhere...

How to make IP forwarding permanent?

Also, this method of configuring a gateway is horribly insecure, and prone to problems that are difficult to anticipate. Have you considered using a tool like Shorewall to configure routing and iptables? Here is a pretty solid howto that would get you started:

http://shorewall.net/three-interface.htm

Community
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le3th4x0rbot
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