IPsec IKEv2 between Cisco 4321 decrypting traffic but not encrypting.

[emurray]

A strange thing has happened on an IPsec configuration. I have done some research with no luck. The tunnel is up, and I did a packet capture on the FortiGate of some icmp packets from the FortiGate to the Cisco and with no response found. I see packets been decrypted on the Cisco side but no encrypted. Here is the configuration on the Cisco router 

crypto ikev2 proposal TestProposal
encryption aes-cbc-256
integrity sha256
group 14

crypto ikev2 keyring Test
peer TestLab
address x.x.x.x
pre-shared-key *******

crypto ikev2 policy TestPolicy
match address local 10.10.15.1
proposal TestProposal

crypto ikev2 profile TestProfile
match identity remote address x.x.x.x x.x.x.x
identity local address x.x.x.x
authentication remote pre-share
authentication local pre-share
keyring local Test

crypto ipsec transform-set Test-set ah-sha-hmac esp-aes
mode tunnel

crypto map Test_MAP 20 ipsec-isakmp
set peer x.x.x.x
set transform-set Test-set
set pfs group14
set ikev2-profile TestProfile
match address Local-To-TestLab


ip access-list extended Local-To-TestLab
permit ip 10.10.15.0 0.0.0.255 192.168.1.0 0.0.0.255

[Rob Ingram · Accepted solution]

@emurray do you have NAT configured that could be unintentionally translating traffic? If so make sure you exclude (deny) the VPN traffic as per the crypto ACL "Local-To-TestLab", to ensure this traffic is not translated.

[emurray]

Thanks for the help. I do have a NAT overload as bellow

Extended IP access list NAT
10 deny ip 10.10.15.0 0.0.0.255 190.85.224.0 0.0.0.255
20 permit ip 10.10.15.0 0.0.0.255 any
30 deny ip any any log

With your suggestion, I did some research and plan to do the following changes

Extended IP access list NAT
10 deny ip 10.10.15.0 0.0.0.255 190.85.224.0 0.0.0.255
15 deny ip 10.10.15.0 0.0.0.255 192.168.1.0 0.0.0.255
20 permit ip 10.10.15.0 0.0.0.255 any
30 deny ip any any log

route-map DenyNAT permit 10
match ip address NAT

ip nat inside source route-map DenyNAT int gi0/0/1 overload

If you see anything wrong, let me know. 

[MHM Cisco World]

....

[emurray]

Wit the changed I posted, I have solved the issue, thanks all for the help. 

[MHM Cisco World]

check the routing and check the exception NAT.