GRE over IPSec ACL question

Bosefus

In all the GRE over IPSec configuration guides I seem to find, they recommend using the following ACL

access-list 120 permit gre host 14.38.88.10 host 14.36.88.6

Where source is outside local and destination is outside remote.

Is the ACL used to specify what traffic to encrypt? If so wont this mean that not all traffic will be encrypted?

Thanks

Ahriakin

It will encrypt whatever you have already encapsulated inside GRE. So if those IPs mark your GRE tunnel endpoints then you ultimately control what actual data is being encrypted by deciding what will go through the GRE tunneling process pre-IPSec.