Hello.

How to solve the case when you have 3 Same networks using different gateways?? I mean,... How Linux kernel will know to deliver the package to the origination network if 3 network are the same?

Ex:
192.168.1.0 netmask 255.255.255.0 gw 192.168.1.23
192.168.1.0 netmask 255.255.255.0 gw 10.0.2.13
192.168.1.0 netmask 255.255.255.0 gw 172.16.1.3

This is NOT fail-over or redundancy... What i want to know if... How Linux will know what gateway use to deliver the package if there are duplicates networks... ??


What i want to do is something like this.

I have 10 interfaces for example:

I want to create an individual routing table for this interface, something like: route -n via eth9

I want to setup individual routing tables without having issue in case duplicates network with others interfaces... is possible?

If all of the systems are on the same networking segment, the gateway won't come into play at all. If they are on different networking segments, you wouldn't use a gateway, as much as adding a route: "ip route add 192.168.1.0/24 dev eth0".


You can have a host with many routes, but everyhost can only have one gateway. It's known as a default route.
Also, you cannot logically (in the networking sense) have two systems on the same layer two network, seperated by a layer three routing device. Hope this helps.

Check this scenario:



VPN SERVER
VPN IP: 172.16.1.1/24


OFFICE#1 LAN
VPN IP: 172.16.1.2
LAN Network: 192.168.1.0/24


OFFICE#2 LAN
VPN IP: 172.16.1.3
LAN Network: 192.168.1.0/24




The VPN Server have this 2 routes

route add -net 192.168.1.0 netmask 255.255.255.0 gw 172.16.1.1
route add -net 192.168.1.0 netmask 255.255.255.0 gw 172.16.1.2

So... The VPN Server will get confused because the network is duplicated. So I imagine, the VPN server will send the package to Both gateways. In this case; 172.16.1.2 and 172.16.1.2.

How can i fix something like this?

The simple answer is, you can't.

A more complex solution might be subnetting, but even then the systems would be on two different networks.
You can have one on the 192.168.1.0/26 network and another on the 192.168.1.64/26 subnet.

Another option would be NATing (Network address Translation), in which case the servers could have the exact same IP. I don't know much about setting NATing up, save grabbing a linksys router or two and throwing it in the mix, hopefully though that will give you some ideas.

Exist a way to create routes using /sbin/route)

Then apply each route ONLY to specify address?