默认情况下帧中继网络是无法运行OSPF协议的，为什么？
【原因】：帧中继（fram-relay）网络属于非广播型多路访问，
而OSPF协议规定路由器之间的Hello包是通过组播来传输
（组播也属于非广播类型）因此帧中继上默认情况是无法运行OSPF协议的。
下面有4种解决方法：
- 方法一，手工设置ospf网络类型为广播型，在指定fram-relay map时设置为broadcast
（Fram-relay 广播） - 方法二，默认非广播类型，使用neighbor手工指定邻居，并且手工指定DR为中心路由器
（fram-relay非广播） - 方法三，手工设置OSPF网络类型为：点到多点型广播型，在指定fram-relay map时设置为broadcast
（fram-relay 点对多点广播） - 方法四：手工设置OSPF网络类型为：点到多点非广播，使用neighbor手工指定邻居
（fram-relay 点对多点非广播）
再看解决方法之前，先理解以下内容
- OSPF中的“neighbor” 可以手动指定邻居路由器的IP地址，使得它不用组播也能和邻居交换路由信息。
- 哪些网络需要选举DR，哪些网络不用选举DR
OSPF网络类型 特征 是否选举DR 广播型多路访问 以太网、令牌环或FDDI 是 非广播型多路访问 帧中继、X.25、SMDS 是 点对点 PPP、HDLC 否 点对多点 由管理员配置 否
3.fram-relay map 中 broadcast 关键词允许路由器通过指定的DLCI号将广播分组分送给所映射的路由器
【实验拓扑】：中心-分支帧中继网络拓扑结构
- 方法一，手工设置ospf网络类型为广播型，在指定fram-relay map时设置为broadcast
R1:interface L0ip address 1.0.0.1 255.0.0.0!interface Serial0/0ip address 10.0.0.1 255.0.0.0encapsulation frame-relayip ospf network broadcastframe-relay map ip 10.0.0.4 104 broadcastframe-relay map ip 10.0.0.5 105 broadcast!router ospf 1network 0.0.0.0 255.255.255.255 area 0R4:interface Ethernet0/0ip address 4.0.0.4 255.0.0.0!interface Serial0/0ip address 10.0.0.4 255.0.0.0encapsulation frame-relayip ospf network broadcastip ospf priority 0frame-relay map ip 10.0.0.1 401 broadcastframe-relay map ip 10.0.0.5 401no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0
R5:interface Ethernet0/0ip address 5.0.0.5 255.0.0.0!interface Serial0/0ip address 10.0.0.5 255.0.0.0encapsulation frame-relayip ospf network broadcastip ospf priority 0frame-relay map ip 10.0.0.1 501 broadcastframe-relay map ip 10.0.0.4 501no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0
- 方法二，默认非广播类型，使用neighbor手工指定邻居，并且手工指定DR为中心路由器
R1:interface Ethernet0/0ip address 1.0.0.1 255.0.0.0!interface Serial0/0ip address 10.0.0.1 255.0.0.0encapsulation frame-relayframe-relay map ip 10.0.0.4 104frame-relay map ip 10.0.0.5 105!router ospf 1network 0.0.0.0 255.255.255.255 area 0neighbor 10.0.0.4neighbor 10.0.0.5R4:interface Ethernet0/0ip address 4.0.0.4 255.0.0.0!interface Serial0/0ip address 10.0.0.4 255.0.0.0encapsulation frame-relayip ospf priority 0frame-relay map ip 10.0.0.1 401frame-relay map ip 10.0.0.5 401no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0R5:interface Ethernet0/0ip address 5.0.0.5 255.0.0.0!interface Serial0/0ip address 10.0.0.5 255.0.0.0encapsulation frame-relayip ospf priority 0frame-relay map ip 10.0.0.1 501frame-relay map ip 10.0.0.4 501no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0
- 方法三，手工设置OSPF网络类型为：点到多点型广播型，在指定fram-relay map时设置为broadcast
R1:interface Ethernet0/0ip address 1.0.0.1 255.0.0.0!interface Serial0/0ip address 10.0.0.1 255.0.0.0encapsulation frame-relayip ospf network point-to-multipointframe-relay map ip 10.0.0.4 104 broadcastframe-relay map ip 10.0.0.5 105 broadcast!router ospf 1network 0.0.0.0 255.255.255.255 area 0R4:interface Ethernet0/0ip address 4.0.0.4 255.0.0.0!interface Serial0/0ip address 10.0.0.4 255.0.0.0encapsulation frame-relayip ospf network point-to-multipointframe-relay map ip 10.0.0.1 401 broadcastno frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0R5:interface Ethernet0/0ip address 5.0.0.5 255.0.0.0!interface Serial0/0ip address 10.0.0.5 255.0.0.0encapsulation frame-relayip ospf network point-to-multipointframe-relay map ip 10.0.0.1 501 broadcastno frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0
- 方法四：手工设置OSPF网络类型为：点到多点非广播，使用neighbor手工指定邻居
R1:interface Ethernet0/0ip address 1.0.0.1 255.0.0.0!interface Serial0/0ip address 10.0.0.1 255.0.0.0encapsulation frame-relayip ospf network point-to-multipoint non-broadcastframe-relay map ip 10.0.0.4 104frame-relay map ip 10.0.0.5 105!router ospf 1network 0.0.0.0 255.255.255.255 area 0neighbor 10.0.0.5neighbor 10.0.0.4R4:interface Ethernet0/0ip address 4.0.0.4 255.0.0.0!interface Serial0/0ip address 10.0.0.4 255.0.0.0encapsulation frame-relayip ospf network point-to-multipoint non-broadcastframe-relay map ip 10.0.0.1 401no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0R5:interface Ethernet0/0ip address 5.0.0.5 255.0.0.0!interface Serial0/0ip address 10.0.0.5 255.0.0.0encapsulation frame-relayip ospf network point-to-multipoint non-broadcastframe-relay map ip 10.0.0.1 501no frame-relay inverse-arp!router ospf 1network 0.0.0.0 255.255.255.255 area 0
本文转自zcm8483 51CTO博客，原文链接:http://blog.51cto.com/haolun/993193
