Cisco NSR be required?

When implementing high-availability stateful switchover BGP routing, in which situation would

Cisco NSR be required?
A . On the PE routers connecting to the CE routers which are not NSF aware or are not NSF
capable
B . On the PE routers connecting to the CE routers which support graceful restart
C . On the PE routers connecting to the CE routers which are incapable of performing stateful switchover operations because the CE routers are only NSF aware but not NSF capable
D . On the PE routers connecting to the CE routers which are incapable of performing stateful switchover operations because the CE routers are only NSF capable but not NSF aware
E . On the service provider core P routers which are also NSF aware
F .  On the service provider core P routers which are also NSF capable

View Answer

Answer: A