Which three characteristics apply to IS - IS but not to OSPF?（）
A. uses a default IOS metric of 10 on each interface
B. uses an on - demand circuit to reduce the hello and LSA flooding across switched WAN li nks,such as ISDN
C. uses a DIS and a backup DIS to present the psuedo - node on the LAN
D. encapsulates PDUs directly into a data - link frame
E. uses stubby areas to improve network scalability
F. runs PRC (Partial Route Calculations) to calculate IP re achability informatio
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