单项选择题
Which protocol is an open standard protocol framework that is commonly used in VPNs,to provid secure end-to-end communication?（）
A. L2TP B. IPsec C. PPTP D. RSA
单项选择题 What is one benefit of PVST+?（）
单项选择题 Which item represents the standard IP ACL?（）
单项选择题 Which statement about access lists that are applied to an interface is true?（）
