Hi everybody

I'm newbie in unix os so, plz, have patience...

I have this issue:

I have a physical machine with only one phisical network card and i have to connect 3 subnet
I have create 3 virtual interface

eth0:1 Link encap:Ethernet HWaddr 00:01:80:68:5A:14
inet addr:85.18.22.33 Bcast:85.18.22.63 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:20 Memory:fdfc0000-fdfe0000

eth0:2 Link encap:Ethernet HWaddr 00:01:80:68:5A:14
inet addr:217.153.107.1 Bcast:217.153.107.31 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:20 Memory:fdfc0000-fdfe0000

eth0:3 Link encap:Ethernet HWaddr 00:01:80:68:5A:14
inet addr:192.168.141.4 Bcast:192.168.141.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:20 Memory:fdfc0000-fdfe0000

connected on layer 2 switch where the network that have access on internet is eth0:3

I have enabled kernel routing in sysclt.cnf

# Controls IP packet forwarding
net.ipv4.ip_forward = 1

and set

iptables -t nat -A POSTROUTING -o eth0:3 -j MASQUERADE

but when i try to connect from a machine on network on eth0:1 to eth0:2 , router put me on real Internet althought routin is as follow

217.153.107.0 * 255.255.255.224 U 0 0 0 eth0
85.18.22.32 * 255.255.255.224 U 0 0 0 eth0
192.168.141.0 * 255.255.255.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 1002 0 0 eth0
default 192.168.141.1 0.0.0.0 UG 0 0 0 eth0

At the end, i would like that machine in network on eth0:1 will no nated on network on eth0:2 but machine on network on eth0:1 and eth0:2 must be nated on eth0:3 because they have to access to real ineternet

Any ideas ?

Thanks for all

PS OS is a CentOS 6

Have you looked into pfsense? I know this can be done with pfsense.

I find a solution so easy so stupid

So, I set a MASQUERADE on eth0 in nat table but for each server in the "false" internet subnet that need to connect the othe "false" internet subnet , i set a SNAT as his original ip

To be more clear

[root@rooter ~]# iptables -t nat -L -n
Chain PREROUTING (policy ACCEPT)
target prot opt source destination

Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
SNAT all -- 85.18.22.36 217.153.107.4 to:85.18.22.36
MASQUERADE all -- 0.0.0.0/0 0.0.0.0/0

Chain OUTPUT (policy ACCEPT)
target prot opt source destination


I hope this can help