A.A value of 4 represents the "Implicit NULL Label."
B.A value of 0 represents the "IPv4 Explicit NULL Label."
C.A value of 1 represents the "Router Alert Label". The use of this label is analogous to the use of the"Router Alert Option" in IP packets （for example， ping with record route option）
D.A value of 2 represents the "IPv6 Explicit NULL Label"
E.A value of 1 represents the "IPv1 Explicit NULL Label"
F.A value of 3 represents the "Implicit NULL Label"

A.it uses multicast address 224.0.0.10，instead of broadcast
B.it uses multicast address 224.0.0.9，instead of broadcast
C.it can use either multicast or broadcast addresses，instead of just broadcast
D.it sends incremental updates，instead of periodic updates
E.it is classless，instead of classful
F.it supports authentication，and RIPv1 does not

A.IBGP updates exchange between trigger router and black hole router
B.EBGP updates exchange between trigger router and black hole router
C.OSPF updates exchange between trigger router and black hole router
D.ISIS updates exchange between trigger router and black hole router

A.The MD5 algorithm inputs the routing updates of arbitrary length and outputs a 128-bit hash
B.The MD5 algorithm inputs the routing updates of every 64bit length and outputs an 8-bit hash
C.Multiple keys are supported
D.Routing updates packets are delivered in encrypted messages
E.Shared secret keys are delivered in encrypted messages

A.Prevents head-of-line blocking
B.Uses less memory
C.Increases forwarding performance
D.Simplifies configuration