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Cisco ASA 5510 Dynamic nat

Posted on 2012-12-28
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Good morning everyone,

We currently have a VPN setup with a client. We now need our home users to access their resources as well. Normally I can just add the home users pool (192.168.253.0) to each end of the tunnel, however the client already has a VPN with a 192.168.253.0. So, my idea is to have the 192.168.253.0/24 translated into 10.66.253.0/24 when it tries to hit the client side (192.168.100.0/24).

I'm pretty sure I need to setup a Dynamic nat policy, but I haven't really done this before. Any help would be beneficial! Thanks
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Question by:prlit
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by:rauenpc
ID: 38727346
What version of ASA do you have? If you have 8.3 or later you can use twice nat. Example:
http://www.fir3net.com/Cisco-ASA/cisco-asa-twice-nat.html

Depending on the complexity of your ASA and network, it might be easier to just change the VPN client pool.
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by:prlit
ID: 38727386
8.2. I could do that for the one client, but our network is pretty complex. I'd have to change about 80+ tunnels to if I change the pool.

Could I do something like..

access-list Exempt permit ip 10.66.253.0 255.255.255.0 192.168.100.0 255.255.255.0
global (inside) 2 10.66.253.0 netmask 255.255.255.0
nat (inside) 2 access-list Exempt

And Of course, add the 10.66.253.0/24 to the tunnels.
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rauenpc earned 2000 total points
ID: 38727565
I think you would need to reference the outside interface, and the ACL would need to reference the original source and real destination. I might be wrong on the outside interface part. I always thought that for vpn it was considered the security level of inside, but nat rules had to reference the real interfaces that traffic was traversing.

access-list Exempt permit ip 192.168.253.0 255.255.255.0 192.168.100.0 255.255.255.0
global (outside) 2 10.66.253.0 netmask 255.255.255.0
nat (outside) 2 access-list Exempt

This should translate the source 192.168.253.0/24 to 10.66.253.0/24 when destined for 192.168.100.0. You are correct about adding the subnet to the tunnel. You will probably need to add a nonat rule for the return traffic so that 192.168.100.0 --> 10.66.253.0 doesn't get translated again.
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Author Closing Comment

by:prlit
ID: 38728286
Thanks! I had it right with my commands, but your outside part I didn't have right. Thanks for your help.
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