Enable Forward Secrecy

From Wikipedia

In Transport Layer Security (TLS), Diffie–Hellman key exchange-based PFSs (DHE-RSA, DHE-DSA) and elliptic curve Diffie–Hellman-based PFSs (ECDHE-RSA, ECDHE-ECDSA) are available.

To achieve this on the BIG-IP then you'll need to amend the Client SSL profile assigned to your virtual servers and prioritise Diffie-Hellman or Elliptic curve Diffie Hellman (or exclude all others of course). There is a lengthy DevCentral post here which will help you: Enabling PFS

Hope this helps,

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