[单选题]11、 Which of the following cannot provide HA or load balancing for VPN connectivity?下面哪一个不能为VPN连接提供HA或者负载平衡?
A. Redundant peering 冗余对等体
B. Active/active failover active/active故障切换
C. Active/standby failover active/standby故障切换
D. Clustering 集群
E. Load balancing using an external ACE 使用外部ACE的负载平衡