A.Flooding paths and redundancy
B.Amount of routing information in the OSPF area or routing domain
C.Number of routers with Cisco Express Forwarding enabled
D.Number of neighbor adjacencies
E.Other routing protocols in use
F.OSPF timer reconstruction negotiation
G.Redistribution with BGP neighbors
H.Redistribution with other IGP routing protocols， such as RIP or EIGRP

A. BGP peers must be Layer 2-adjacent
B. EBGP multihop is not configured
C. The firewall is not configured to allow IP protocol 89
D. The firewall is not configured to allow UDP 179.