1.何时产生 |
1.1实验拓扑 |
1.2实验需求 (1)按拓扑完成基本配置 (2)R2、R3间运行OSPF,R2上写一条静态路由,ip route 10.10.10.0 255.255.255.0,并重分发进OPSF进程 (3)指定其下一跳为31.31.12.100,观察AS External LSA中的Forwarding Address (4)将R2所连31.31.12.0网段宣告进OSPF进程,观察实验现象 (5)将静态路由只指定出口,观察实验现象 (6)静态路由指定出口加上下一跳,观察实验现象 (7)R2上创建loopback 0 2.2.2.2/24,并且在OSPF进程中重分发直连,观察实验现象 |
1.3实验步骤 (1)静态路由 R2(config)#ip route 10.10.10.0 255.255.255.0 31.31.12.100
R2(config-router)#redistribute static subnets
R2#show ip ospf database external | in Forward Forward Address: 0.0.0.0 此时,值被置为0.0.0.0
(2)接口参与OSPF R2(config-router)#network 31.31.12.2 0.0.0.0 a 0
R2#show ip ospf database external | include Forward Forward Address: 31.31.12.100 此时,LSA Type 5中的Forward Address继承了静态路由中该网络的下一跳,即便实际中该下一跳不存在
(3)静态路由只指定出口 R2(config)#no ip route 10.10.10.0 255.255.255.0 R2(config)#ip route 10.10.10.0 255.255.255.0 fa0/0
R2#show ip ospf database external | include Forward Forward Address: 0.0.0.0 此时,转发地址在此被置为0.0.0.0
(4)出口加上下一跳 R2(config)#no ip route 10.10.10.0 255.255.255.0 R2(config)#ip route 10.10.10.0 255.255.255.0 fa0/0 31.31.12.100
R2#show ip ospf database external | include Forward Forward Address: 31.31.12.100 再次继承
(5)创建环回口网络,重分发直连 R2(config)#inter lo 0 R2(config-if)#ip add 2.2.2.2 255.255.255.0 R2(config)#router ospf 1 R2(config-router)#redistribute connected subnets
R2#show ip ospf database external
OSPF Router with ID (2.2.2.2) (Process ID 1)
Type-5 AS External Link States
LS age: 9 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 2.2.2.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0x632F Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0
LS age: 129 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 10.10.10.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0x28A3 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 31.31.12.100 External Route Tag: 0 |
1.4实验结论 (1)重分发进OSPF进程的外部网络 ①如果原本不存在下一跳,则Forward Address为0.0.0.0,表示为通告者ASBR本身 ②如果存在下一跳: a.如果下一跳所在网段参与OSPF进程,则Forward Address将继承该下一跳 b.如果下一跳所在网段未参与OSPF进程,则Forward Address为0.0.0.0 |
2.原路由负载均衡 |
2.1实验拓扑 |
2.2实验需求 (1)按拓扑完成基本配置 (2)R1上将EIGRP网络重分发进OSPF进程,观察LSA Type 5中的Forward Address (3)R1上将连接EIGRP域的接口加入到OSPF进程中,观察实验现象 |
2.3实验步骤 (1)重分发EIGRP R1#show ip route eigrp 10.0.0.0/24 is subnetted, 1 subnets D 10.10.10.0 [90/156160] via 31.31.123.3, 00:00:49, FastEthernet0/0 [90/156160] via 31.31.123.2, 00:00:49, FastEthernet0/0 R1去往10.10.10.0网络负载均衡
R1(config)#router ospf 1 R1(config-router)#redistribute eigrp 1 subnets
R1#show ip ospf database external
OSPF Router with ID (1.1.1.1) (Process ID 1)
Type-5 AS External Link States
LS age: 76 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 10.10.10.0 (External Network Number ) Advertising Router: 1.1.1.1 LS Seq Number: 80000001 Checksum: 0x601E Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0
LS age: 76 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 31.31.123.0 (External Network Number ) Advertising Router: 1.1.1.1 LS Seq Number: 80000001 Checksum: 0x7171 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0 此时的Forward Address值为0.0.0.0
(2)接口参与OSPF R1(config)#router ospf 1 R1(config-router)#network 31.31.123.1 0.0.0.0 a 0
R1#sho ip rou ei 10.0.0.0/24 is subnetted, 1 subnets D 10.10.10.0 [90/156160] via 31.31.123.3, 00:00:01, FastEthernet0/0 [90/156160] via 31.31.123.2, 00:00:01, FastEthernet0/0
R1#show ip ospf database external
OSPF Router with ID (1.1.1.1) (Process ID 1)
Type-5 AS External Link States
LS age: 25 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 10.10.10.0 (External Network Number ) Advertising Router: 1.1.1.1 LS Seq Number: 80000002 Checksum: 0x9927 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 31.31.123.3 External Route Tag: 0 此时只带有一个转发地址 |
2.4实验结论 当原路由有多个下一跳时,选择IP地址最大的作为转发地址 |
3.转发地址与接口网络类型 |
3.1实验拓扑 |
3.2实验需求 (1)按拓扑完成基本配置 (2)R1开启OSPF进程,宣告直连网络进入OSPF,重分发RIP进入OSPF,观察LSDB (3)修改接口网络类型为Non-Broadcast,观察LSDB (4)修改接口网络类型为Point-to-Point,观察LSDB (5)修改接口网络类型为Point-to-Multipoint,观察LSDB |
3.3实验步骤 (1)完成需求(2) R1#show ip ospf interface f0/0 | include Network Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
R1#show ip ospf database external | in Forward Forward Address: 31.31.12.2 当接口网络类型为广播时,外部路由会带上转发地址
(2)完成需求(3) R1(config-if)#ip ospf network non-broadcast
R1#show ip ospf interface f0/0 | include Network Process ID 1, Router ID 1.1.1.1, Network Type NON_BROADCAST, Cost: 1
R1#show ip ospf database external | in Forward Forward Address: 31.31.12.2 当接口网络类型为非广播时,外部路由会带上转发地址
(3)完成需求(4) R1(config-if)#ip ospf network point-to-point
R1#show ip ospf interface f0/0 | include Network Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
R1#show ip ospf database external | in Forward Forward Address: 0.0.0.0 当接口网络类型为点到点时,外部路由转发地址为0.0.0.0
(4)完成需求(5) R1(config-if)#ip ospf network point-to-multipoint
R1#show ip ospf interface f0/0 | include Network Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 1
R1#show ip ospf database external | in Forward Forward Address: 0.0.0.0 当接口网络类型为点到多点时,外部路由转发地址为0.0.0.0
注意: 当修改为点到多点非广播类型时,现象与点到多点相同 |
3.4实验结论 当接口网络类型为点到多点以及点到点时,不会携带非0转发地址 |