多项选择题
Which three authentication options does IS-IS support?（）
A. MD5 B. DES C. Kerberos D. unauthenticated E. simple password
多项选择题 In which two ways can you influence how downstream LSRs treat MPLS traffic?（）
多项选择题 Which three are well-known mandatory BGP attributes? （）
单项选择题 How long is an IPv6 address?（）
