帧中继网络中配置OSPF

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

1. 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。
2. 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 L0

ip address 1.0.0.1 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.1 255.0.0.0

encapsulation frame-relay

ip ospf network broadcast

frame-relay map ip 10.0.0.4 104 broadcast

frame-relay map ip 10.0.0.5 105 broadcast

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

R4:

interface Ethernet0/0

ip address 4.0.0.4 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.4 255.0.0.0

encapsulation frame-relay

ip ospf network broadcast

ip ospf priority 0

frame-relay map ip 10.0.0.1 401 broadcast

frame-relay map ip 10.0.0.5 401

no frame-relay inverse-arp

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

 

R5:

interface Ethernet0/0

ip address 5.0.0.5 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.5 255.0.0.0

encapsulation frame-relay

ip ospf network broadcast

ip ospf priority 0

frame-relay map ip 10.0.0.1 501 broadcast

frame-relay map ip 10.0.0.4 501

no frame-relay inverse-arp

!

router ospf 1

network 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 Ethernet0/0

ip address 1.0.0.1 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.1 255.0.0.0

encapsulation frame-relay

frame-relay map ip 10.0.0.4 104

frame-relay map ip 10.0.0.5 105

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

neighbor 10.0.0.4

neighbor 10.0.0.5

R4:

interface Ethernet0/0

ip address 4.0.0.4 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.4 255.0.0.0

encapsulation frame-relay

ip ospf priority 0

frame-relay map ip 10.0.0.1 401

frame-relay map ip 10.0.0.5 401

no frame-relay inverse-arp

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

R5:

interface Ethernet0/0

ip address 5.0.0.5 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.5 255.0.0.0

encapsulation frame-relay

ip ospf priority 0

frame-relay map ip 10.0.0.1 501

frame-relay map ip 10.0.0.4 501

no frame-relay inverse-arp

!

router ospf 1

network 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 Ethernet0/0

ip address 1.0.0.1 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.1 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint

frame-relay map ip 10.0.0.4 104 broadcast

frame-relay map ip 10.0.0.5 105 broadcast

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

R4:

interface Ethernet0/0

ip address 4.0.0.4 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.4 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint

frame-relay map ip 10.0.0.1 401 broadcast

no frame-relay inverse-arp

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

R5:

interface Ethernet0/0

ip address 5.0.0.5 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.5 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint

frame-relay map ip 10.0.0.1 501 broadcast

no frame-relay inverse-arp

!

router ospf 1

network 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 Ethernet0/0

ip address 1.0.0.1 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.1 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint non-broadcast

frame-relay map ip 10.0.0.4 104

frame-relay map ip 10.0.0.5 105

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

neighbor 10.0.0.5

neighbor 10.0.0.4

R4:

interface Ethernet0/0

ip address 4.0.0.4 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.4 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint non-broadcast

frame-relay map ip 10.0.0.1 401

no frame-relay inverse-arp

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

R5:

interface Ethernet0/0

ip address 5.0.0.5 255.0.0.0

!

interface Serial0/0

ip address 10.0.0.5 255.0.0.0

encapsulation frame-relay

ip ospf network point-to-multipoint non-broadcast

frame-relay map ip 10.0.0.1 501

no frame-relay inverse-arp

!

router ospf 1

network 0.0.0.0 255.255.255.255 area 0