文章目录
P2P(Point-to-Point 点对点)P2MP(Point ti Multi-Point 点到多点)BMA(Broadcast Multiple Access 广播多路访问）NBMA(Non-Broadcast Multiple Access 非广播多路访问)OSPF网络类型是一个非常重要的接口变量，这个变量将影响OSPF在接口上的操作，例如采用什么方式发送OSPF协议报文，以及是否需要选举DR、BDR等。OSPF有4种网络类型，分别是P2P、P2MP、BMA(Broadcast)、NBMA。OSPF网络类型的影响：一般情况下，链路两端的OSPF接口网络类型必须一致，否则双方无法建立邻居关系。
P2P(Point-to-Point 点对点)
P2P指的是在一段链路上只能连接两台网络设备的环境，一根网线，一左一右。该环境下只有2台设备，也只能是2台设备，链路中间不能加入其他设备。如，一条链路上不能加入交换机设备。典型的例子是PPP链路。当接口采用PPP封装时，OSPF在该接口上采用缺省网络类型是P2P。P2MP(Point ti Multi-Point 点到多点)
P2MP相当于将多条P2P链路的一段进行捆绑得到的网络。没有一种链路层协议会被缺省的认为是P2MP网络类型。该类型必须由其他网络类型手动更改。常用的做法是将非全连通的NBMA改为点到多点的网络。P2MP示例图
MA,Multi-Access,多路访问网络有2种类型：广播型多路访问网络（BMA）和非广播型多路访问（NBMA）
BMA(Broadcast Multiple Access 广播多路访问）
BMA也被称为Broadcast，指的是一个允许多台设备接入的、支持广播的环境。典型的例子是Ethernet以太网。当接口采用Ethernet封装时，OSPF在该接口上采用的缺省网络类型为BMA。NBMA(Non-Broadcast Multiple Access 非广播多路访问)
NBMA指的是一个允许多台网络设备接入且不支持广播的环境。典型的例子是帧中继（Frame-Relay）网络。OSPF网络类型可以在接口下通过命令手动修改以适应不同网络场景，如可以将BMA网络类型修改为P2P。
示例：
# 配置完接口，默认是BMA[AR1-GigabitEthernet0/0/0]dis this[V200R003C00]#interface GigabitEthernet0/0/0ip address 10.1.12.1 255.255.255.0 #return#查看可以修改的网络类型[AR1-GigabitEthernet0/0/0]ospf network-type ?broadcast Specify OSPF broadcast networknbma Specify OSPF NBMA networkp2mp Specify OSPF point-to-multipoint networkp2p Specify OSPF point-to-point network#修改为P2P，重新建立邻居关系[AR1-GigabitEthernet0/0/0]ospf network-type p2pFeb 16 21:54:50-08:00 AR1 %%01OSPF/3/NBR_CHG_DOWN(l)[8]:Neighbor event:neighbor state changed to Down. (ProcessId=256, NeighborAddress=2.2.2.2, NeighborEvent=KillNbr, NeighborPreviousState=Full, NeighborCurrentState=Down) [AR1-GigabitEthernet0/0/0][AR1-GigabitEthernet0/0/0]Feb 16 21:54:50-08:00 AR1 %%01OSPF/3/NBR_DOWN_REASON(l)[9]:Neighbor state leaves full or changed to Down. (ProcessId=256, NeighborRouterId=2.2.2.2, NeighborAreaId=0, NeighborInterface=GigabitEthernet0/0/0,NeighborDownImmediate reason=Neighbor Down Due to Kill Neighbor, NeighborDownPrimeReason=Interface Parameter Mismatch, NeighborChangeTime=-02-16 21:54:50-08:00) [AR1-GigabitEthernet0/0/0]Feb 16 21:54:56-08:00 AR1 %%01OSPF/4/NBR_CHANGE_E(l)[10]:Neighbor changes event: neighbor status changed. (ProcessId=256, NeighborAddress=2.12.1.10, NeighborEvent=HelloReceived, NeighborPreviousState=Down, NeighborCurrentState=Init) [AR1-GigabitEthernet0/0/0]Feb 16 21:54:56-08:00 AR1 %%01OSPF/4/NBR_CHANGE_E(l)[11]:Neighbor changes event: neighbor status changed. (ProcessId=256, NeighborAddress=2.12.1.10, NeighborEvent=2WayReceived, NeighborPreviousState=Init, NeighborCurrentState=ExStart) [AR1-GigabitEthernet0/0/0]Feb 16 21:54:56-08:00 AR1 %%01OSPF/4/NBR_CHANGE_E(l)[12]:Neighbor changes event: neighbor status changed. (ProcessId=256, NeighborAddress=2.12.1.10, NeighborEvent=NegotiationDone, NeighborPreviousState=ExStart, NeighborCurrentState=Exchange) [AR1-GigabitEthernet0/0/0]Feb 16 21:54:56-08:00 AR1 %%01OSPF/4/NBR_CHANGE_E(l)[13]:Neighbor changes event: neighbor status changed. (ProcessId=256, NeighborAddress=2.12.1.10, NeighborEvent=ExchangeDone, NeighborPreviousState=Exchange, NeighborCurrentState=Loading) [AR1-GigabitEthernet0/0/0]Feb 16 21:54:56-08:00 AR1 %%01OSPF/4/NBR_CHANGE_E(l)[14]:Neighbor changes event: neighbor status changed. (ProcessId=256, NeighborAddress=2.12.1.10, NeighborEvent=LoadingDone, NeighborPreviousState=Loading, NeighborCurrentState=Full)
