NAT RULE - IPsec VPN

[joseglez]

Hello all,

I am implementing an IPsec VPN and I have to NAT the source IP address, but I am very confused with the bidirectional source NAT,

Lets say my local IP=192.168.1.1 (natted to 1.1.1.1), remote IP in the other side of the VPN= 10.10.10.1

For example If I configure:

Src Zone        Src IP                  Dest Zone            Dest. IP             NAT 

Internal          192.168.1.1            VPN                 10.10.10.1        source nat: 1.1.1.1   (bidirectional)

behind the scene the returning NAT rule created will be:

Src Zone        Src IP                  Dest Zone            Dest. IP             NAT 

Any                   Any                       VPN                     1.1.1.1              dest. nat: 192.168.1.1 

My confusion is based in the fact that 1.1.1.1 is not in the VPN zone, its a external IP in the External zone so I think I cannot use bidirectional NAT in this scenario and I have to create 2 rules for each direction like:

Src Zone        Src IP                  Dest Zone            Dest. IP             NAT 

Internal          192.168.1.1            VPN                 10.10.10.1            source nat: 1.1.1.1 

Src Zone        Src IP                  Dest Zone            Dest. IP             NAT 

 VPN              10.10.10.1             External               1.1.1.1              dest. nat: 192.168.1.1 

Am I wrong about this?

[SutareMayur]

@joseglez,

First of all, is it bidirectional tunnel (both sides will be initiator and responder) then only you need BI-Directional NAT ?

If only any of the side is initiator and other responder, then you don't need Bi-Directional NAT.

Now you want to NAT IP 192.168.1.1 with 1.1.1.1, in this case,

1. IP 1.1.1.1 shouldn't be part of VPN ZONE. Destination IP addresses will be part of VPN zone (i.e. 10.10.10.1 ). Just make sure you have route towards desired tunnel interface for this IP/network.

2. Configure proper NAT Rule. So IP 1.1.1.1 would be consider to be part of internal as it is going to DNAT with internal IP 192.168.1.1

3. Also make sure NAT IP 1.1.1.1 is part of proxy ID configuration.

Hope it helps you!

Mayur

[joseglez]

Hello @SutareMayur,

Yes, it will be bidirectional.

I agree with you when you said that 1.1.1.1 shouldn't be in the  VPN. Since that is what paloalto would do if I select bidirectional source NAT,

that is why I think I may have to use 2 unidirectional rules.

I do not quite understand when you said that: "IP 1.1.1.1 would be consider to be part of internal as it is going to DNAT with internal IP 192.168.1.1"

Do you mean, when creating the reverse rule, instead of external I should put Internal as  dest zone??

[SutareMayur · Accepted solution]

@joseglez,

Yes, for reverse rule (inbound traffic), you need to put destination zone as internal not external. Then only traffic will be forwarded to internal IP 192.168.1.1. Normally while hosting internal server also, we configure policies in same way.

Your NAT would be like -

Bi-Directional NAT

SZONE - Internal

S-IP - 192.168.1.1

DZONE - VPN

D-IP - 10.10.10.1

S-NAT-IP - 1.1.1.1

Security Policy for outbound traffic -

SZONE - Internal

S-IP - 192.168.1.1

DZONE - VPN

D-IP - 10.10.10.1

Security Policy for inbound traffic -

SZONE - VPN

S-IP - 10.10.10.1

DZONE - Internal

D-IP - 1.1.1.1

Also configure proper routes and proxy-id configuration. With this, everything should work as expected.

Hope it helps!

Mayur

[joseglez]

Great, thank you @SutareMayur 

I included the after NAT IPs in the proxy IDs also.