This won't work though. Because returning packets to the client are going to appear to come from a different address. He's not doing any sort of NAT, and since it's a transition, the box will have to answer to request going to it's real IP besides the ones that come from the forwarding rule. As far as I know, there's not any easy way to do it except maybe to create a tunnel between the two boxes, and then do source routing. I don't know if linux will do source routing though, never tried it. Jay > -----Original Message----- > From: Thomas J. Hudak [mailto:thudak at autonomous.tv] > Sent: Tuesday, December 04, 2001 12:12 PM > To: tclug-list at mn-linux.org > Subject: Re: [TCLUG] Port forwarding to other networks > > > * Brian (lxy at cloudnet.com) wrote: > > I'm moving a machine from building A to building B. > Building A has a > > T1 and building B has a DSL. Since there's lots of DNS > stuff pointed > > to its address on the T1 it will take some time to get it > all moved to > > the DSL. Here's my thought: I have a few extra linux boxen on the > > building A T1. Can I bind the old IP address to one of > these and port > > forward it to the box over in building B? That way I have > very little > > down time while my DNS changes get propogated. I can't > find anything > > on doing this in the ipfwadm or ipmasqadm docs. > Yes, and it's quite easy. > > Since I'm using a real network-os (/me ducks), I'll give you > an ipfw rule that will work, then you'll at least have an > idea of what it's supposed to look like, and should be able > to translate it to iptables-speak. > > ipfw add forward all 1.2.3.4 80 4.3.2.1 1337 in via xl0 > > On a BSD box with IPFW enable, that says "forward all types > of traffic from 1.2.3.4 on port 80 to 4.3.2.1 port 1337 > coming in via xl0" > Which gives the added bonus of *only* forwarding all the data > that comes > *in* to the desired ethernet device for that address/port. > > head over to linuxdoc.org, last I checked they had some good > tutorials on ipmasq/chains/tables to peruse... the iptables > lines are similar in syntax enought that it shouldn't be too hard. > > Good luck, and post again if you still have problems > > Thomas J. Hudak > Professional Unix Admin for hire > > _______________________________________________ > Twin Cities Linux Users Group Mailing List - Minneapolis/St. > Paul, Minnesota http://www.mn-linux.org > tclug-list at mn-linux.org > https://mailman.mn-> linux.org/mailman/listinfo/tclug-list >