不定项选择题 5.  DMVPNs can use pre-shared keys or PKI-based IKE authentication. Either choice is acceptable for a hub-and-spoke network, but which of the following is recommended for a fully meshed network? DMVPN支持使用预共享密钥或基于PKI的IKE认证。对于中心到分支模型的拓扑，这两种认证方法都是可接受的；但是对于全互连模型的拓扑，你应当优选使用以下哪项认证方法?