在配置NBMA的情況下，OSPF在同一時刻向每一個路由器只會傳送一個Hello包（Hello包周期性傳送，用於建立和確定路由間的鄰居關係）而不是進行多播。Hello包的傳送周期間隔的範圍為10s~30s，而判斷鄰居失效(dead)的時間範圍為40s~120s（4倍於Hello包傳送間隔）。
NBMA (non-broadcast multiple access)is one of four network types in the OSPF (Open Shortest Path First) communications protocol. NBMA is used to accurately model X.25 and frame relay environments in multiple-access networks where there are no intrinsic broadcast and multicast capabilities. The other OSPF network types are: broadcast, point-to-point, and point-to-multipoint. In an NBMA configuration, OSPF sends HELLO packets (packets sent periodically to establish and confirm neighbor relationships between routers) to each router one at a time rather than multicasting them. The HELLO timer (which tells the router how often to send HELLO packets) is extended from 10 to 30 seconds and the dead router timer (which tells the router how long to wait before it decides that a neighboring router is not functioning) is extended from 40 to 120 seconds.
