A.The TCP connection that matches the defined ACL will be reset by the router if the connection does not complete the three-way handshake within the defined time period.
B.The router will reply to the TCP connection requests. If the three-way handshake completes successfully， the router will establish a TCP connection between itself and the server.
C.The TCP traffic that matches the ACL will be allowed to pass through the router and create a TCP connection with the server.
D.The router will intercept the traceroute messages. It will validate the connection requests before forwarding the packets to the inside network.

A.RRI
B.IPsec Backup Peerings 
C.Dynamic Crypto Ma
D.HSRP
E.IPsec Stateful Switchover （SSO）
F.Dual Router Mode （DRM） IPsec