Many thanks tomaskir, I made the change however still no luck. I'm starting to think the issue is with the config on the ASA side and not the Mikrotik.

Hi there I am trying to create a VPN tunnel using IPSEC between a Mikrotik router and a Cisco ASA. However I cant get the tunnel to come up. The client has confirmed all is correct on their ASA. My config is as follows: x.x.x.x = Cisco ASA y.y.y.y = Mikrotik Public IP a.a.a.a = Mikrotik internal net...