Multiple NICs different subnets

tecbox · 03-20-2010, 10:12 AM

I've got a Linux box on my network with multiple NIC cards. One of the network cards is in the 192.168.0.0 subnet and the other is in the 192.168.2.0 subnet. The router on my network (Dlink 655) has an IP of 192.168.0.2 and has network filtering enabled. The logs on my router are filled with "Access denied to LAN system with MAC address xx:xx:xx:xx:xx:xx" for the NIC on the 192.168.2.0 subnet.

Is this to be expected? Can I configure the NIC on the 192.168.2.0 subnet to prevent it from accessing the router? The NIC on the 192.168.2.0 subnet is connected to a switch and only needs access to another box on the same subnet and therefore, does not need access to the router.

This is the route table on the linux box:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.3.0     *               255.255.255.0   U     0      0        0 eth0
192.168.2.0     *               255.255.255.0   U     0      0        0 eth1
192.168.0.0     *               255.255.255.0   U     0      0        0 eth2
169.254.0.0     *               255.255.0.0     U     0      0        0 eth2
default         192.168.0.1     0.0.0.0         UG    0      0        0 eth2

Thanks.

pingu · 03-20-2010, 11:19 AM

If eth2 doesn't need access to the router, then I suppose it's connected to a switch where comp no2 also is connected? This should be no problem!
However, if you connect that switch to the router you'll have problems.
As far as I know, the only way to get the traffic for 192.168.2.x through router is to set 2 ip:s on the routers interface. In Linux no problem, don't know about your router.

tecbox · 03-20-2010, 04:42 PM

Thanks for the reply.

Yes, both of the boxes that have the 192.168.2.0 subnet IP's are connected to the switch and the switch is connected to the router. These two boxes with the 192.168.2.0 subnet IP's do NOT need access to the router, they just need to talk to each other.

I'd just like to prevent the massive amount of access attempts that these boxes try to make with the router.

jefro · 03-21-2010, 05:56 PM

To not access the router you remove gateway setting I'd think.

pingu · 03-22-2010, 03:30 AM

No, that doesn't work - if you remove gateway for 192.168.2.x then all traffic to that subnet will be sent through eth2.
Actually, with switch connected to router traffic willbe sent to router as well. To stop that you would need a more advanced/managed switch. But why not simply either disconnect switch from router or connect the 2 boxes directly wo switch? (Guessing now you only have 2 computers on 192.168.2.x)