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

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 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