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mr.b
Asked: 2010-07-09 00:44:08 +0800 CST

Port forwarding from non-default internet connection

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I have two outgoing connections, pointing to different ISPs, on a gateway, in front of small-ish LAN.

IPs addresses are as follows:

ISP 1:

  • network: 10.1.1.0/24
  • gateway ip: 10.1.1.1
  • client ip: 10.1.1.2 (eth1)

ISP 2:

  • network: 10.2.1.0/24
  • gateway ip: 10.2.1.1
  • client ip: 10.2.1.2 (eth2)

LAN:

  • network: 192.168.0.0/24
  • gateway ip: 192.168.0.1 (eth0)

Few LAN clients, with IPs in range 192.168.0.128/25.

So, essentially, gateway has IPs 10.1.1.2, 10.2.1.2, and 192.168.0.1 on 3 NICs.

Default route on gateway is set to 10.1.1.1 dev eth1.

Right now, I have one routing table consisting of following entries, named isp2:

  • network 192.168.0.0/24 dev eth0
  • network 10.2.1.0/24 dev eth2
  • default route 10.2.1.1 dev eth2

I use that isp2 in MANGLE rules to redirect some traffic to utilize second outgoing link.

Everything works fine, when I want to redirect traffic that goes OUT, if it will go over primary ISP or over secondary ISP, based on MANGLE table rules.

Question: How do I configure gateway so it would allow inbound connections from second ISP, to be forwarded to clients in LAN, behind gateway? I want to forward traffic incoming on specific ports to specific port of specific clients, but it has to work over non-default route.

Any ideas?

Platform that I use is irrelevant, I'm more interested what needs to be done in order for this to work, but you can write examples as if I were using linux (so iproute2/iptables).

routing port-forwarding

1 Answers

  1. Best Answer

    You may use rinetd.

    For FTP forwarding via ISP2, while ISP1 is the default one.

    oneliner config:

    10.2.1.2:21 192.168.1.129:21

    the downside: on your FTP log, all connections will appear as coming from 10.2.1.2

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