单项选择题
What are the default values for GRE tunnel keeplive time and number of retries？（）
A.5 seconds and 3 retries B.10 seconds and 5 retries C.10 seconds and 3 retries D.20 seconds and 5 retries E.5 seconds and 5 retries
单项选择题 HowmanymessagesdoesInternetKeyExchangeusetonegotiateSAcharacteristicwhenitrunsinaggressivemode？（）
单项选择题 WhichstatementaboutSNMPistrue？（）
多项选择题 InrelationtoMPLSMulticastVPN，whichthreestatementsaboutmulticastdistribution（MDT）groupsaretrue？（）
