OSPF and NAT

Answered Question
Mar 9th, 2007
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We bought out another company and are connecting our networks. Unfortunately their numbering clashes with one of our own.


I am planning on setting up NAT on their router to NAT their addressing to something else but have a question regarding OSPF. I need OSPF to propagate the NATTED subnet and not their true subnet.


Is this possible?


Denny

Correct Answer by paolo bevilacqua about 10 years 3 months ago

Absolutely possible. From the router that does NAT, the subnet can be originated as external - "redistribute static subnets".


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dennylester Mon, 03/12/2007 - 15:12
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Bump..


Is this possible?


If not, any recommendations? We use OSPF to maintain floating static routes for DDR backups.


Renumbering one of the subnets is not an option at the moment.


Denny



Correct Answer
paolo bevilacqua Mon, 03/12/2007 - 15:27
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Absolutely possible. From the router that does NAT, the subnet can be originated as external - "redistribute static subnets".


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dennylester Mon, 03/12/2007 - 16:06
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That is exactly what I was looking for.


Thank you,


Denny

dennylester Mon, 03/12/2007 - 16:52
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Okay, I guess I need more help.


How do I redistribute a static subnet or inject a subnet into OSPF to be propagated?


I've used the redistribute static command before, but I actually had a route in my routing table.


On the NAT router, this subnet solely exists in a NAT translation.


Thanks,


Denny

sundar.palaniappan Mon, 03/12/2007 - 17:21
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You can configure a static route to point to the null0 interface like this one;


ip route <172.16.1.0 255.255.255.0> null0


This would cause the route to be put into the routing table as a static route. Substitute the IP with your NAT IP.


HTH


Sundar

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