Linux router with diffent gateways for incomming and outgoing connections

Posted by nkout on Server Fault See other posts from Server Fault or by nkout
Published on 2012-04-05T14:04:12Z Indexed on 2012/04/06 11:33 UTC
Read the original article Hit count: 210

Filed under:

linux

|

iptables

|

routing

I have the following topology:

LAN Users:192.168.1.2 - 254 (192.168.1.0/24)
gateway1: 192.168.2.2/24 used for all outgoing connections of LAN users (default gateway)
gateway2: 192.168.3.2/24 used for incoming services (destination NAT, ports 80,443 are forwarded to 192.168.2.1)
linux router-server R
- eth0 192.168.1.1/24: LAN
- eth1 192.168.2.1/24: WWAN1
- eth2 192.168.3.1/24: WWAN2

I want to:

route all outgoing traffic coming from LAN and R via 192.168.2.2
route the responses to incoming connections via 192.168.3.2

My config:

ifconfig eth0 up 192.168.1.1 netmask 255.255.255.0
ifconfig eth1 up 192.168.2.1 netmask 255.255.255.0
ifconfig eth2 up 192.168.3.1 netmask 255.255.255.0
echo 0 >/proc/sys/net/ipv4/ip_forward
route add default gw 192.168.2.2
iptables -t nat -A POSTROUTING -d !192.168.0.0/16 -j MASQUERADE

I want to add iptables rule to mark incoming traffic from WWAN2 and send back the responses to WWAN2, while keeping default gateway on WWAN1

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