configuration proxy arp and forwarding

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Oct 15th, 2008
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Hello.

How can I forward traffic from LAN 192.168.0.0/24 to 192.168.2.0/24 when the source 192.168.0.20 want to connect to the server 192.168.1.20

but this server is physical in the lan 192.168.2.0/24 and his real IP is 192.168.2.20.

The Backbone-Router routes traffic only between 192.168.0.0/24 and 192.168.1.0/24. I have only access to configure the Cisco-Router.


[LAN 192.168.0.0/24]<-->[BackBone-Router]<-->[LAN 192.168.1.0/24]<-->[Cisco Router]<-->[LAN 192.168.2.0/24]


All I need is a suggestion.

Best regards.

Olaf

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Jon Marshall Wed, 10/15/2008 - 02:49
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Is 192.168.1.20 in use on the 192.168.1.0/24 LAN already. if not



LAN 192.168.0.0/24]<-->[BackBone-Router]<-->[LAN 192.168.1.0/24]<--> (int fa0/1)[Cisco Router](int fa0/0) -> [LAN 192.168.2.0/24]


On the Cisco router


ip nat inside source static 192.168.2.20 192.168.1.20


int fa0/0

ip nat inside


int fa0/1

ip nat outside


The above will NAT 192.168.2.20 to 192.168.1.20 for all traffic. If you just want it to be Natted for 192.168.0.20 then you need policy NAT. Let me know if you need this.


Jon

obachmann Wed, 10/15/2008 - 03:08
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Hello Jon.


The 192.168.1.20 is not used in the lan 172.20.1.0.


In your example the router have to answer for arp request for the IP 172.20.2.20. Is the default interface setting "ip proxy-arp" enought?


Olaf

Jon Marshall Wed, 10/15/2008 - 03:57
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Olaf


Sorry, where has the 172.20.1.0 network come from ?


Jon

obachmann Wed, 10/15/2008 - 04:38
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Ups ;-)

I wanted to write "The 192.168.1.20 is not used in the lan 192.168.1.0".


My mistake.

Olaf

Jon Marshall Wed, 10/15/2008 - 07:14
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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 192.168.1.20 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 :)


Jon

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