configuration proxy arp and forwarding

Unanswered Question
Oct 15th, 2008


How can I forward traffic from LAN to when the source want to connect to the server

but this server is physical in the lan and his real IP is

The Backbone-Router routes traffic only between and I have only access to configure the Cisco-Router.

[LAN]<-->[BackBone-Router]<-->[LAN]<-->[Cisco Router]<-->[LAN]

All I need is a suggestion.

Best regards.


I have this problem too.
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Jon Marshall Wed, 10/15/2008 - 02:49

Is in use on the LAN already. if not

LAN]<-->[BackBone-Router]<-->[LAN]<--> (int fa0/1)[Cisco Router](int fa0/0) -> [LAN]

On the Cisco router

ip nat inside source static

int fa0/0

ip nat inside

int fa0/1

ip nat outside

The above will NAT to for all traffic. If you just want it to be Natted for then you need policy NAT. Let me know if you need this.


obachmann Wed, 10/15/2008 - 03:08

Hello Jon.

The is not used in the lan

In your example the router have to answer for arp request for the IP Is the default interface setting "ip proxy-arp" enought?


obachmann Wed, 10/15/2008 - 04:38

Ups ;-)

I wanted to write "The is not used in the lan".

My mistake.


Jon Marshall Wed, 10/15/2008 - 07:14

When you add the NAT commands the router knows it has to answer arp requests for that IP address. So the router will see the arp request for and because it has a static NAT translation for that it will respond to the arp with it's own mac-address.

Glad it was a typo, i thought i was losing the plot :)



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