How to forward a port to CISCO in substitution of the departure address?

Question

Computer networks

There is a cisco 2801 router with two interfaces, ip external 87.1.1.1, ip internal 192.168.0.1, internal server 192.168.0.200, port 80
. sending 192.168.0.1 and at the same time an entry appeared in the translation table to return it back, in a normal ip translation, the departure address does not change. Needed to access the server from a backup channel without reconfiguring the default route.

Answer 1

Port forwarding, or Port forwarding, should look something like this:
should work

Answer 2

As I understand it, you want the internal server to see the router itself as the source of the packet?
But then the router will in any case send the packet to the real sender according to the routing table, and not the translation table.
You need to do Policy Based Routing.

Answer 3

ip nat inside source static tcp 192.168.0.200 80 87.1.1.1 80 extendable
in this case, the packet arrives at the host with a real source ip, since it comes from the outside of the interface and will return to the default gateway specified on the host.
But if you are accessing from a static IP, you can add a route on the host towards the backup channel and, accordingly, the packet will return to where it came from.

Answer 4

On Windows, for example, the command
netsh interface portproxy add v4tov4 listenport=3389 listenaddress=xxxx connectport=3389 connectaddress=yyyy
does just that.
That is, in the packet within the network, the return address is the internal Windows address of the gateway, and not the address of the client on the Internet.