Problem of nat

Unanswered Question
Aug 30th, 2007
User Badges:

sorry for my english, i'm french ...;

I wish that since my lan when I enter my publicip address with port I?m redirect towards the nat which correpond with the interface wan.


My router is configured for nat since the interface Wan port 80 towards private address IP 80. I wish that when I type the Ippublique address: 80 since my lan that is redirected towards the nat correpondant lan with the address: 80.

I wish that if my nat on the interface Wan with port 6589 is configured for router on the local address : 56, that when I type my ippublic address with port 6589 since my lan that I is directly to redirect towards the address room corresponds 56.

I have to test on several occasions different config but ever succeeded. Best will be than the rule is dynamic that wants right statement than this ?loopback? between interface is automatically realizable on all the redirections of port between the interface wan and lan interfaces it.

thank you in advance.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (3 ratings)
mheusing Thu, 08/30/2007 - 04:14
User Badges:
  • Cisco Employee,


May I try to rephrase your requirement as far as I understand it - sorry if I misunderstood, I am not french ;-)

You have workstations in your LAN, which should access some servers locally using the official IP address.

One different approach than NAT: use DNS.

In your inside DNS server resolve the server name to your private IP. In case there is no internal DNS server, use the workstations host file to resolve the name.

Any solution natting your official IP to a private one for your LAN hosts would also forward all traffic through your router. This would slow down transfer and put additional CPU load to your router.

The DNS/hostname approach will allow to forward traffic directly and looks preferable to me. In case you have requirements ruling out the DNS approach, please describe them and we go from there.

Regarding the port redirection: What would prevent you from using the port (f.e. 56) directly?

Hope this helps! Please rate all posts.

Regards, Martin

wififrance Thu, 08/30/2007 - 05:23
User Badges:

yes i'am in the case there is no internal DNS server. my Dns server is the dns of my ISP i give you a little shema. ( shema. jpg)

i'am connected on the web server with the host D: i see my webpage with ip adresse public ( the router is configured for natting the on the All it's ok i can see my web page.

now i want to see my page with the host A but with the external adresse ( ). I am on the host A, i open my web browser and i want to see the web page in the server web by the adresse When i enter this adresse in the browser of the host A they have ? message : ERROR 404 by internet explorer. I look for an acl or what ever for redirected automatiquely the traffic with the rules of nat.

This behavior are configurated automatiquely in the factory settings on Linksys router WAG54G.But i can't find this configuration on a Cisco 877.

Please your are my last chance . tks so much

wififrance Thu, 08/30/2007 - 06:34
User Badges:

i look for the commande for active the Nat loopback. do you know this commande ? tks a lot


This Discussion