Port forwarding question

[pkluss]

I have an interesting network setup that I'm dealing with. Let's say my we've been issued a public block of IPs 200.200.200.200 - 200.200.200.215. Our internal network address is ALSO 200.200.200 We're basically using NAT as a firewall, but we don't manage our router, our ISP does. Naturally, they don't like having to make changes for us, and technically aren't required to, but they have obliged anyway. Now, we have another smaller intranet that has the address 192.168.192, and this is where all of our servers are. So far we have only NATted to the servers with simple lines like

ip nat inside source static udp 192.168.192.10 2944 200.200.200.205 2944 extendable

Now we're coming across a scenario where we need to NAT through to an internal address that unfortunately is of an external IP that we do not own. Let's say that IP is 200.200.200.250. Someone else owns the public IP, and we're fine with that, but will the router know that we mean for it to let the packets through to the internal IP or will it send them back out? I've read something about an overlay as well, is that related? I basically want to get all of this straight BEFORE I call the ISP since they aren't obligated to do any of it at all. They keep threatening to turn over the management of the router to me and I'd like to defer as long as I can. So, can you help me make it easy for them? Is this possible?

Thanks.

P.S. - Feel free to comment on the ridiculous setup that we have. I really would like to hear why our overall setup is or isn't a good idea, but please also answer the question.

 

[SQL2KDBA69]

so is the ip 200.200.200.250 on the public interface of your router. what do you mean u dont own the ip?

 

[BlitzCan]

Not sure how big your network is, but if it's feasible time-wise, you may want to change the internal addresses, preferably non-routable blocks like 192.168.x.x, 172.x.x.x or 10.x.x.x.

Cheers!

 

[BlitzCan]

I thought I should mention that when I try and telnet into the router on port 25 from an external connection, it isn't rejected. Instead, it appears to connect, but then the cursor just sits there, and key inputs dont echo. Eventually, the connection drops though. I'm familiar with the "200 *****************" response from fixup smtp, but this is truly bizarre. If I try to telnet on any other port, it simply gets rejected, which tells me that something is happening on port 25.

Oh, and telnet port 25 connections to the actual server's internal IP are fine, and are greeted with the usual Exchange messages. So, that's not the problem either.

Thanks again!

 

[BlitzCan]

Ignore the above... accidentally posted into wrong thread. Sorry!