Route packets by source IP

["Steffen Heil" <lists@steffen-heil.de>]

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Hi

I have two servers, having public IPs A1, B1, connected via private IPs A2,
B2 on a openVPN network.
Now I need to make a service (port p) of server A1:p available via B1:p.
So I want to try the following:

1. At B: dnat every incoming connection for B1:p to A2:p.
    - this is to archieve my goal -
2. At A: Route every packet "from A2:P" to B2.
    - otherwise A would try to route to the client via its gateway, which
would fail because of the private sender ip. -

I think I can do the first:

iptables -t nat -I PREROUTING -p tcp --dport p -j DNAT --to A2:p

But I don't know how to do the second.
Any hints?

Regards,
  Steffen

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