Passing Client certificate to pool members for authentication

in this case C3D, i need to create a CA and that need to be configured on the server ssl profile and have to import on the server trust store as well. F5 will re-sign the client cert and send to serve for authentication, when it re-signs the server will use the locally generate CA or real client cert for authentication?. bit confused here. if using local CA generate means, then what's the point of client authentication on server side.