An LTM device pair is configured for failover and connection mirroring. The LTM devices are configured with virtual servers for HTTP, HTTPS with SSL offload, and SSH. An event occurs that causes a failover. HTTP and SSH sessions active at the time of failover remain active, but HTTPS sessions are dropped.
What is the root cause of this problem?
The root cause of the problem is that connection mirroring was not enabled for the HTTPS virtual servers. Connection mirroring ensures that sessions persist after a failover occurs. In this case, although HTTP and SSH sessions remain active, the HTTPS sessions drop because the SSL-specific data required to maintain the HTTPS sessions was not mirrored to the peer device.
why not D ?
Should be D - K17391: Configuring SSL connection mirroring for Client SSL virtual servers
This case, like everything in the dump, is considered in the 11.4 version of Big-IP. In the article above, SSL connection mirroring is possible starting from version 12.
D - Correct In BIG-IP 12.0.0 and later, you can configure the system to mirror SSL connections that are terminated by the BIG-IP system to peer device group members. When you enable connection mirroring on a virtual server that references an SSL profile, the BIG-IP system mirrors SSL-specific data to the appropriate device group member. This preserves SSL connections when failover occurs. https://my.f5.com/manage/s/article/K17391