* 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