Server not reachable from internal network when using portforwarding

Unanswered Question
May 10th, 2007

Hi all,

i have newbie question. We have the following situation:

A brachnoffice in Hungary is connected to our headoffice in Germany via IPSEC-VPN. Everything is working fine, all necessary traffic goes through the tunnels.

But if i set up a port forwarding (port 443) on the Router (1812) in Hungary to a server in the hungarian network, i cannot reach the server over the internal network from Germany. The port forwarding is working but if i use a private address from internal just the used port is not working.

Do you have any hints for me??

Thanks for your help

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bjornarsb Thu, 05/10/2007 - 05:42


your problen is this:

access-list 103 deny tcp any host $PUBLIC_IP eq 443

applied on:


interface FastEthernet1

description Interface zum Provider

ip address $PUBLIC_IP

ip access-group 103 in

ip nat outside

ip virtual-reassembly

duplex auto

speed auto

crypto map Erlangen


HTH, rate if it does.



smallore_4plus Thu, 05/10/2007 - 05:50


thanks for the fast response, but i don?t think that this entry is the problem, because i also tested it with an other port (1677).

I used a second public IP-Address (which we also bought) for the port forwarding.


bjornarsb Thu, 05/10/2007 - 05:58


But try disabling your acl for a very short period and see if it works :)



smallore_4plus Fri, 05/11/2007 - 23:36

Hi again,

i did what you said and removed the complete access-list 103 and then it works from internal and external.

But can you tell me which statement is blocking the internal requests? Or do you know a debug setting which can tell me what is the reason for the blocking?

Thank for now.

Greetings Alex

bjornarsb Sat, 05/12/2007 - 07:35

Hi mate,

That was good news!

OK if you want to see which statement is blocking you need to enable logging of your acl's statement.

like this :


access-list 1 permit log

access-list 1 deny log




access-list 1 permit log-input

access-list 1 deny log-input.

HTH,rate if it does



smallore_4plus Mon, 05/14/2007 - 02:32

OK, thanks for the hint.

Do you see, maybe, an error in the access-list? Or will i need further statements to allow the access??



smallore_4plus Mon, 05/14/2007 - 11:00

Hi again,

i have bad news. I tried again to disable the access-list to check what statement is blocking my requests, but this times after applying the portforwading rule (ip nat inside source static tcp internal_IP 443 external_IP 443) i had also no internal access to the server.

I have no idea to fix that problem... :o(

Maybe someone else???

Best gegards


bjornarsb Mon, 05/14/2007 - 23:54


Which ip do you use from the inside, when you try to access your server. You cannot use de global DNS name (i.e the external_IP )

You either need an internal dns or edit the host file on your computers.




smallore_4plus Tue, 05/15/2007 - 00:18


i use from internal.

We also have a working DNS. I want to use the same DNS-Name from internal and from external. The internal DNS should point to the internal address and an official DNS-Record should point to the external, public IP.



smallore_4plus Tue, 05/15/2007 - 04:43

Without the portforwarding this works, after applying the statement it doesn?t work.


smallore_4plus Wed, 05/30/2007 - 04:42

Hi again,

i was away for a week on vacation.

I think the problem is the communication between Germany and Hungary over VPN, because if i insert the portforwarding statement the server is reachable from the internet and from the local network in Hungary. But from the german Network it cannot be reached.

Do somebody see my mistake in the configuration??

Thanks in advance



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