What will be happen to live and existing connections when failover HA BIG IP active-standby

Zen_Y 

When a failover occurs, all existing connection will be reset because the newly active device is not aware of the existing connections to the previous active device. please find below a knowledge based article that explains this.

K14203: Active connections may experience a long delay following failover

https://my.f5.com/manage/s/article/K14203

Hope this helps