[Gllug] routing via a second external IP

[John Winters]

Paul Cupis wrote:
[snip]
> 
> No, but if you have two DSL connections (seperate, each with their own 
> IP(s), and you route specific traffic (by IP or port) down the second 
> one (the first being default route), then that traffic will return via 
> the same connection and thus NAT will work just fine.

Yes, but that's not the case being talked about here.  The OP asked for
a solution where the connection is initiated from *outside*.  Which
incoming link is used will therefore be dictated by what IP address the
outside initiator uses.  If that doesn't agree with the way the internal
routing tables are set up then you'll end up with traffic coming in down
one link and out down the other.  Even this will work only if the target
internal machine has a real IP address, or all NATing is performed
entirely behind the merge point of the two links.  If NATing is done on
the links individually (or on one and not the other) then connections
simply won't work.

There was an earlier claim made in the thread that it is possible to
control which link the incoming traffic will come down by using iproute2
on the gateway box, but we've yet to see any justification of that
claim.  I'm not familiar with iproute2, but given the requirement to
control the behaviour of routers out there on the 'net before you even
know the connection is coming I don't believe it's possible.

John
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