Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 4 OSPF Configuration4-4aggregated into one route 19.1.0.0/16, and only one corresponding LSA, whichdescribes the route after summary, is generated on RTA.Router AABR Router BABR Area 019.1.1.0/2419.1.2.0/2419.1.3.0/24……Area 119.1.0.0/16Figure 4-1 Area partition and route aggregation4.1.4 OSPF Network TypesI. Four OSPF network typesOSPF divides networks into four types by link layer protocols:z Broadcast: If Ethernet or FDDI is adopted, OSPF defaults the network type tobroadcast. In a broadcast network, protocol packets are sent in multicast(224.0.0.5 and 224.0.0.6) by default.z Non-broadcast multi-access (NBMA): If Frame Relay, ATM, or X.25 is adopted,OSPF defaults the network type to NBMA. In an NBMA network, protocolpackets are sent in unicast.z Point-to-multipoint (P2MP): OSPF will not default the network type of any linklayer protocol to P2MP. A P2MP network must be compulsorily changed fromanother network type. The common practice is to change an NBMA network intoa P2MP network. In a P2MP network, protocol packets are sent in multicast(224.0.0.5).z Point-to-point (P2P): If PPP or HDLC is adopted, OSPF defaults the networktype to P2P. In a P2P network, protocol packets are sent in multicast (224.0.0.5).II. Principles for configuring an NBMA networkAn NBMA network is a non-broadcast and multi-accessible network. ATM and framerelay networks are typical NBMA networks.Some special configurations need to be done on an NBMA network. In an NBMAnetwork, an OSPF router cannot discover an adjacent router by broadcasting Hellopackets. Therefore, you must manually specify an IP address for the adjacent routerand specify whether the adjacent router can vote for a DR.An NBMA network must be fully connected. That is, any two routers in the networkmust be directly reachable to each other through a virtual circuit. If two routers in thenetwork are not directly reachable to each other, you must configure thecorresponding interface type to P2MP. If a router in the network has only one peer,you can change the corresponding interface type to P2P.The differences between NBMA and P2MP are as follows:
