帧中继多点子接口下配置OSPF

1、实验目的

通过本实验可以掌握

A、帧中继多点子接口的特征

B、帧中继多点子接口的配置

C、NBMA模式下OSPF的配置和调试

D、手工配置OSPF邻居

E、NBMA模式下的DR选举

2、实验拓扑

3、实验步骤

本实验分别在路由器R1、R3和R4尚创建多点子接口，拓扑结构采用Hub-and-Spoke结构，整个网络运行OSPF路由协议。

A.配置路由器R1

R1(config)#int loopback0

R1(config-if)#ip address 192.168.1.1 255.255.255.0

R1(config-if)#no shutdown

R1(config-if)#ip ospf networkpoint-to-point //修改OSPF网络类型

R1(config-if)#exit

R1(config)#int s1/0

R1(config-if)#no ip address //物理接口下不要配置IP地址

R1(config-if)#encapsulation frame-relay //接口封装帧中继

R1(config-if)#no frame-relay inverse-arp //关闭帧中继逆向ARP解析

R1(config-if)#no shutdown

R1(config-if)#exit

R1(config)#int serial 1/0.1 multipoint //创建帧中继多点子接口

【技术要点】

“int serial slot-number/interface-number.subinterface-number{ multipoint|point-to-point }”命令用来创建帧中继子接口，其中：

1）slot-number/interface-number：物理接口的号；

2）subinterface-number：是自接口号，范围为1~4 294 967 293；

3）multipoint |point-to-point：属于必须选择的项，是子接口的类型，要么是多点类型，要么是点到点类型。

R1(config-subif)#ip address 192.168.134.1 255.255.255.0

R1(config-subif)#frame-relay map ip 192.168.134.3 103broadcast

R1(config-subif)#frame-relay map ip 192.168.134.4 104broadcast

R1(config-subif)#frame-relay map ip 192.168.134.1 103

R1(config-subif)#no frame-relay inverse-arp

R1(config-subif)#exit

R1(config)#router ospf 1

R1(config-router)#router-id 1.1.1.1

R1(config-router)#network 192.168.1.0 0.0.0.255 area 0

R1(config-router)#network 192.168.134.0 0.0.0.255 area 0

R1(config-router)#neighbor 192.168.134.3 //手工指定OSPF邻居

R1(config-router)#neighbor 192.168.134.4

B.配置路由器R3：

R3#conf t

Enterconfiguration commands, one per line. End with CNTL/Z.

R3(config)#intlo0

R3(config-if)#ipaddress 192.168.3.1 255.255.255.0

R3(config-if)#noshutdown

R3(config-if)#ipospf network point-to-point

R3(config-if)#exit

R3(config)#ints1/1

R3(config-if)#noip address

R3(config-if)#encapsulationframe-relay

R3(config-if)#noframe-relay inverse-arp

R3(config-if)#noshutdown

R3(config-if)#exit

R3(config)#ints1/1.1 multipoint

R3(config-subif)#ipaddress 192.168.134.3 255.255.255.0

R3(config-subif)#ipospf priority 0

//配置spoke端OSPF接口优先级为0，确保HUB端路由器R1成为DR

R3(config-subif)#frame-relaymap ip 192.168.134.1 301 broadcast

R3(config-subif)#frame-relaymap ip 192.168.134.4 301 broadcast

R3(config-subif)#frame-relaymap ip 192.168.134.3 301

R3(config-subif)#noframe-relay inverse-arp

R3(config-subif)#exit

R3(config)#routerospf 1

R3(config-router)#router-id3.3.3.3

R3(config-router)#network192.168.134.0 0.0.0.255 area 0

R3(config-router)#network192.168.3.0 0.0.0.255 area 0

【提示】

可以使用“no interfaceSerial1/1.1”命令来删除子接口。然而需要重新启动路由器，该子接口才真正被删除。

C.配置路由器R4：

R4#conf t

Enterconfiguration commands, one per line. End with CNTL/Z.

R4(config)#intlo0

R4(config-if)#ipaddress 192.168.4.1 255.255.255.0

R4(config-if)#ipospf network point-to-point

R4(config-if)#noshutdown

R4(config-if)#exit

R4(config)#ints1/2

R4(config-if)#noip address

R4(config-if)#encapsulationframe-relay

R4(config-if)#noframe-relay inverse-arp

R4(config-if)#noshutdown

R4(config-if)#exit

R4(config)#ints1/2.1 multipoint

R4(config-subif)#ipaddress 192.168.134.4 255.255.255.0

R4(config-subif)#ipospf priority 0

R4(config-subif)#frame-relaymap ip 192.168.134.1 401 broadcast

R4(config-subif)#frame-relaymap ip 192.168.134.3 401 broadcast

R4(config-subif)#frame-relaymap ip 192.168.134.4 401

R4(config-subif)#noframe-relay inverse-arp

R4(config-subif)#exit

R4(config)#routerospf 1

R4(config-router)#router-id4.4.4.4

R4(config-router)#network192.168.134.0 0.0.0.255 area 0

R4(config-router)#network192.168.4.0 0.0.0.255 area 0

D．帧中继交换机配置：

R2#conf t

Enterconfiguration commands, one per line. End with CNTL/Z.

R2(config)#frame-relayswitching

R2(config)#ints1/0

R2(config-if)#clockrate 64000

R2(config-if)#encapsulationframe-relay

R2(config-if)#nosh

R2(config-if)#frame-relaylmi-type cisco

R2(config-if)#frame-relayintf-type dce

R2(config-if)#frame-relayroute 103 interface s1/1 301

R2(config-if)#frame-relayroute 104 interface s1/2 401

R2(config-if)#exit

R2(config)#ints1/1

R2(config-if)#clockrate 64000

R2(config-if)#encapsulationframe-relay

R2(config-if)#noshutdown

R2(config-if)#frame-relaylmi-type cisco

R2(config-if)#frame-relayintf-type dce

R2(config-if)#frame-relayroute 301 interface s1/0 103

R2(config-if)#exit

R2(config)#ints1/2

R2(config-if)#clockrate 64000

R2(config-if)#encapsulationframe-relay

R2(config-if)#frame-relaylmi-type cisco

R2(config-if)#frame-relayintf-type dce

R2(config-if)#frame-relayroute 401 interface s1/0 104

R2(config-if)#

【技术要点】

1）在帧中继网络上，OSPF接口默认的网络类型为NON_BROADCAST。在这种模式下，OSPF不会在帧中继接口上发送Hello包，因此无法建立最基本的OSPF邻接关系。可以手工使用“neighbor”命令来指定邻居，这时Hello包以单播形式发送。

2）NBMA属于多路访问网络，所以要进行DR选举，由于Hello包只能传1跳，所以在Hub-and-Spoke结构中，必须控制处于“HUB”端的路由器成为DR，最保险的办法就是将“Spoke”端路由器OSPF接口优先级配置为0，使之不参与DR选举，“HUB”端的路由器自然就成为DR；否则，可能会导致路由学习不正常。

3）在接口模式下，可以通过如下命令修改OSPF的网络类型：

R3(config-if)#ip ospf network { broadcast | point-to-point| non_broadcast | point-to-multipoint }

4）多点子接口不能解决接口水平分割的问题，只是节省了物理接口而已。

4、实验调试

1）show frame-relay map

R1#showframe-relay map

Serial1/0.1(up): ip 192.168.134.1 dlci 103(0x67,0x1870), static,

CISCO, status defined, active

Serial1/0.1(up): ip 192.168.134.3 dlci 103(0x67,0x1870), static,

broadcast,

CISCO, status defined, active

Serial1/0.1(up): ip 192.168.134.4 dlci 104(0x68,0x1880), static,

broadcast,

CISCO, status defined, active

R1#

以上输出表明路由器R1使用多点子接口S1/0.1，该子接口下有3条帧中继静态映射。

2）show ip ospf interface

R1#showip ospf interface

Serial1/0.1is up, line protocol is up

Internet Address 192.168.134.1/24, Area 0

Process ID 1, Router ID 1.1.1.1, Network TypeNON_BROADCAST, Cost: 64

//接口网络类型为NBMA模式

Transmit Delay is 1 sec, State DR, Priority 1

//状态为DR，接口优先级为1

Designated Router (ID) 1.1.1.1, Interfaceaddress 192.168.134.1

//DR的ID和接口地址

No backup designated router on this network

//没有BDR

Timer intervals configured, Hello 30, Dead120, Wait 120, Retransmit 5

//NBMA模式下，Hello间隔为30S，Dead保持时间为120S

oob-resync timeout 120

Hello due in 00:00:10

Supports Link-local Signaling (LLS)

Index 2/2, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 1, maximum is 1

Last flood scan time is 0 msec, maximum is 4msec

Neighbor Count is 2, Adjacent neighbor countis 2

//有2个OSPF邻居，都形成了邻接关系

Adjacent with neighbor 3.3.3.3

Adjacent with neighbor 4.4.4.4

//以上两行表明路由器R1与路由器R3和R4形成邻接关系

Suppress hello for 0 neighbor(s)

3）show ip route

R1#showip route ospf

O 192.168.4.0/24 [110/65] via 192.168.134.4,00:40:37, Serial1/0.1

O 192.168.3.0/24 [110/65] via 192.168.134.3,00:40:37, Serial1/0.1

R1#

R3#showip route ospf

O 192.168.4.0/24 [110/65] via 192.168.134.4,00:41:32, Serial1/1.1

O 192.168.1.0/24 [110/65] via 192.168.134.1,00:41:32, Serial1/1.1

R3#

R4#showip route ospf

O 192.168.1.0/24 [110/65] via 192.168.134.1,00:42:10, Serial1/2.1

O 192.168.3.0/24 [110/65] via 192.168.134.3,00:42:10, Serial1/2.1

R4#