O F篇：帧中继承载O F-广播

文章作者 100test 发表时间 2007:09:06 11:28:46
来源 100Test.Com百考试题网

　　目标：

　　在R1，R4和R5之间的帧中继网络中配置OSPF，网络类型为broadcast，实现VLAN A， VLAN B和VLAN C的互通

　　配置指南：

　　在R1上配置接口Ethernet0/0地址为1.0.0.1/8

　　在R4上配置接口Ethernet0/0地址为4.0.0.4/8

　　在R5上配置接口Ethernet0/0地址为5.0.0.5/8

　　在R1上配置接口Seria0/0地址为10.0.0.1/8

　　在R4上配置接口Serial0/0地址为10.0.0.4/8

　　在R5上配置接口Serial0/0地址为10.0.0.5/8

　　在R1，R4和R5的Serial接口上配置帧中继封装

　　在R4和R5上禁用帧中继反向地址解析

　　在R1上配置静态映射，通过DCLI104到10.0.0.4和通过DLCI105到10.0.0.5

　　在R4上配置静态映射，通过DLCI401到10.0.0.1和10.0.0.5

　　在R5上配置静态映射，通过DLCI501到10.0.0.1 和10.0.0.4

　　确保链路支持广播和多播数据包传递

　　在R1， R4， 和R5的Serial接口上配置OSPF网络类型为broadcast

　　在R4和R5配置Serial接口OSPF优先级为0

　　配置R1， R4和R5中所有接口加入area 0

　　自我提问：

　　broadcast的网络类型和其他网络类型有什么不同？

　　这种网络类型中LSA是单播还是组播发送？

　　这种网络类型支持DR/BDR 选举吗？

　　这些属性对配置有什么影响？

　　最终配置和验证：

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 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 R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.0.0.4 0 FULL/DROTHER 00:00:33 10.0.0.4 Serial0/0 10.0.0.5 0 FULL/DROTHER 00:00:36 10.0.0.5 Serial0/0 R4#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.0.0.1 1 FULL/DR 00:00:39 10.0.0.1 Serial0/0 R5#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.0.0.1 1 FULL/DR 00:00:33 10.0.0.1 Serial0/0 R1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Ethernet0/0 O 4.0.0.0/8 [110/74] via 10.0.0.4, 00:01:49, Serial0/0 O 5.0.0.0/8 [110/74] via 10.0.0.5, 00:01:49, Serial0/0 C 10.0.0.0/8 is directly connected, Serial0/0 R4#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set O 1.0.0.0/8 [110/74] via 10.0.0.1, 00:02:26, Serial0/0 C 4.0.0.0/8 is directly connected, Ethernet0/0 O 5.0.0.0/8 [110/74] via 10.0.0.5, 00:02:26, Serial0/0 C 10.0.0.0/8 is directly connected, Serial0/0 R5#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set O 1.0.0.0/8 [110/74] via 10.0.0.1, 00:00:11, Serial0/0 O 4.0.0.0/8 [110/74] via 10.0.0.4, 00:00:11, Serial0/0 C 5.0.0.0/8 is directly connected, Ethernet0/0 C 10.0.0.0/8 is directly connected, Serial0/0

　　注解：

　　在网络类型为broadcast的网络中OSPF hellos包是通过组播传递，像non-broadcast的网络类型一样需要DR/BDR 的选举。对于以太网络或者令牌网这种广播型网络来说，这种是缺省的网络类型。需要注意的是本例中的framerelay map命令增加了broadcast选项，这是因为hello包是组播传递的。另外由于不是单播所以对于DR和BDR就不需要配置neighbor的命令。同样还会出现前例讲到的优先级配置问题，略过。

　　通过使用show ip ospf neighbor命令来验证邻居关系，使用show ip ospf interface命令来验证网络类型和DR/BDR.

　　关于下一跳的问题也类似前例。