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Fundamental network question NAT

Amafsha1
Level 2
Level 2

I apologize for asking a question that I should probably know the answer too, but was just wondering if there is a trick that can be done here.

 

Is it possible to have 2 different public IP addresses resolve to the same internal IP address?

 

So I have the same website that resolves to 2 different URLs example: abc.com and cba.com both resolve to 172.28.250.2 internally.  Was wondering if lets say these 2 URLs from the public Internets perspective resolve to 2 different IP address lets say 67.67.67.67 and 68.68.68.68 could I somehow write a NAT statment that could get them to both external ips to resolve to 172.28.250.2 and work someway?  This is in the case that I don't have the ability to change the DNS.

 

Sorry for the bad question

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Accepted Solutions

balaji.bandi
Hall of Fame
Hall of Fame

If you have other basic running config and NAT in place.

 

ip nat inside source static tcp 172.28.250.2  67.67.67.67 80  - here given example you are using http service
ip nat inside source static tcp 172.28.250.2  68.68.68.68 80  - here given example you are using http service

tweak the config based on your requirement. 

BB

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View solution in original post

NAT in a way is like proxy arp, in the way it responds to multiple IP addresses on the same device, so you can have NAT to two public IP addresses and translate/NAT those two IP addresses two the same inside local IP address. It is not very common, but certainly possible.

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View solution in original post

7 Replies 7

balaji.bandi
Hall of Fame
Hall of Fame

If you have other basic running config and NAT in place.

 

ip nat inside source static tcp 172.28.250.2  67.67.67.67 80  - here given example you are using http service
ip nat inside source static tcp 172.28.250.2  68.68.68.68 80  - here given example you are using http service

tweak the config based on your requirement. 

BB

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so this actually works?  This won't cause any funny routing problems?

 

Thank you for your response

NAT in a way is like proxy arp, in the way it responds to multiple IP addresses on the same device, so you can have NAT to two public IP addresses and translate/NAT those two IP addresses two the same inside local IP address. It is not very common, but certainly possible.

Please remember to rate useful posts, by clicking on the stars below.

Thank you sir.  But would you agree that DNS would be the better way to go instead of doing this?

Yes if you have 2 host names that ultimately resolve to the SAME internal server, then there is no need to use two separate public IPs for that. just create two A records for the dns names and resolve them into the same public IP

Please remember to rate useful posts, by clicking on the stars below.

Sure as per the original post i was in impression you have 2 Public IP from different ISP, you want to use DNS entries.

but if you looking domain1.com and domain2.com to point to single Public IP that is possible, its again based on your requirement.

 

my original suggestion based on your post.

 

BB

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i was just told that they want the 2 different URLs with the 2 different external IPs to be used for accessing the same website because they want 2 ways to get into the website (management purposes...) that I don't understand.   So I guess I'm making another NAT statment for this new public IP to resolve our internal IP

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