Two routers running Cisco IOS Software are failing to negotiate the IPsec tunnel. Crypto debugs reveal the following messages:

1d00h: IPSec(validate_transform_proposal): proxy identities not supported 1d00h: ISAKMP: IPSec policy invalidated proposal 1d00h: ISAKMP (0:2): SA not acceptable!

What is the most likely cause of the error message? Select the best response.

A.
Crypto access lists are not mirrored on each side.

B.
The crypto-map is incomplete.

C.
ISAKMP policies have attributes that do not match.

D.
This is not an error message, but an indication that proxy IDs are not supported.