GRE over IPSec tunnel between two routers having overlapped subnets

[gauravshar]

Hi there,

I wish to create a GRE over IPsec tunnel between two routers which have overlapping subnets in their respective LANs. Please let me know if that would be OK to implement and will work. I understand there are some problems with NAT related to encrypted traffic and we can use IPSec tunnel (not GRE over IPsec) in this scenario. I want to make sure whether GRe over IPsec would work too.

Gaurav

[gauravshar]

not implemented yet.. but the below post says 'Yes', 'ip nat outside' at tunnel interface is very much possible:

https://supportforums.cisco.com/thread/77316

Let me see when I actually implement it..

Gaurav

[Maykol Rojas]

Hello,

Nat occurs before encryption, so the answer is Yes, you will need to Nat one of the local networks on one of the endpoints in order to accomplish this configuration.

Cheers

Mike