Private networks fail to communicate with each other after IPSec is configured. The possible causes are as follows:
The public addresses of two IPSec-enabled devices cannot ping each other.
The data flow defined for IPSec encapsulation is the same as that defined for NAT. You can run the display acl all command to view the matching ACL rule. In this case, use either of the following methods to prevent the data flow overlapping:
Ensure that the destination IP address in the ACL rule referenced by IPSec is denied in the ACL rule referenced by NAT. By doing so, the device does not perform NAT on the data flow protected by IPSec.
The ACL rule referenced by IPSec matches NAT-translated IP address.
The device incorrectly learns private routes. The outbound interface to the destination private network is not the public network interface with IPSec enabled.