There is a lot of unknown in your question.
If there is no router between your F5 and your DC, then unless both, your F5 and your DC's are using the same CIDR mask 21 (255.255.248.0), they won't see each other.
If you ping your DC from F5 shell? Just want to see if they can see each other via their respective default routes. You might try traceroute as well, to see where your traffic is being routed or dropped.