目的一, R3实现负载均衡:
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
O
1.1.1.1 [110/65] via 13.1.1.1, 00:00:36, Serial1/0
2.0.0.0/32 is subnetted, 1 subnets
O
2.2.2.2 [110/65] via 23.1.1.2, 00:00:36, Serial2/0
3.0.0.0/24 is subnetted, 1 subnets
C
3.3.3.0 is directly connected, Loopback0
23.0.0.0/24 is subnetted, 1 subnets
C
23.1.1.0 is directly connected, Serial2/0
12.0.0.0/24 is subnetted, 1 subnets
O
12.1.1.0 [110/128] via 23.1.1.2, 00:00:36, Serial2/0
[110/128] via 13.1.1.1, 00:00:36, Serial1/0
13.0.0.0/24 is subnetted, 1 subnets
C
13.1.1.0 is directly connected, Serial1/0
配置完成,正确选路.开销为64+64=128
目的二, 分别更改R1和R2 在12.1.1.0/24 网络的COST值, 影响R3选路:
R2(config)#int s2/0
R2(config-if)#ip ospf cost 110
R1(config)#int s1/0
R1(config-if)#ip ospf cost 100
毫无疑问,这里R3到达12.1.1.0/24 网络要通过COST小的,也就是R1.
R3#
12.0.0.0/24 is subnetted, 1 subnets
O
12.1.1.0 [110/164] via 13.1.1.1, 00:24:14, Serial1/0
这证明:
OSPP里所有路由器的动作,是计算自己所有OSPF接口/链路的COST值,并通过
LSA-1通告出去! 同时把受到的到达各个网络的COST值 (包括自己链路) 相加,
选择最优的装进路由表.
目的三, 我们先来看一下OSPF的数据库, 了解LSA-1里面的一些内容:
R3#show ip ospf database router
OSPF Router with ID (3.3.3.3) (Process ID 10)
Router Link States (Area 0)
LS age: 556
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 1.1.1.1
Advertising Router: 1.1.1.1
LS Seq Number: 80000007
Checksum: 0x5BEE
Length: 84
Number of Links: 5
Link connected to: a Stub Network
(Link ID) Network/subnet number: 12.1.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 100
LS age: 1168
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 2.2.2.2
Advertising Router: 2.2.2.2
LS Seq Number: 80000005
Checksum: 0xCB4E
Length: 84
Number of Links: 5
Link connected to: a Stub Network
(Link ID) Network/subnet number: 12.1.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 110
R3 只是提取到同一网络最小 Metrics值,再和自己计算的链路COST, 做累加
100+64=164,装进路由表!
目的四, R1上加一台路由R4, 相当于:R4=>R1=>R2=>R3 串连, 拓扑如下:
R4正确配置, DOWN掉R1的S2/0端口,现在我们来看一下, R4到达3.3.3.0/24网络,
采用的是R1的100? 还是R2的110 ? 反之, R3到4.4.4.0/24 呢 ?
R4通过E0/0 连接R1, 并宣告进OSPF区域0:
R4#
router ospf 10
router-id 4.4.4.4
network 4.4.4.0 0.0.0.255 area 0
network 14.1.1.0 0.0.0.255 area 0
R4#show ip route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
O
1.1.1.1 [110/11] via 14.1.1.1, 00:05:49, Ethernet0/0
2.0.0.0/32 is subnetted, 1 subnets
O
2.2.2.2 [110/111] via 14.1.1.1, 00:05:49, Ethernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O
3.3.3.3 [110/175] via 14.1.1.1, 00:05:49, Ethernet0/0
4.0.0.0/24 is subnetted, 1 subnets
C
4.4.4.0 is directly connected, Loopback0
23.0.0.0/24 is subnetted, 1 subnets
O
23.1.1.0 [110/174] via 14.1.1.1, 00:05:49, Ethernet0/0
12.0.0.0/24 is subnetted, 1 subnets
O
12.1.1.0 [110/110] via 14.1.1.1, 00:05:49, Ethernet0/0
14.0.0.0/24 is subnetted, 1 subnets
C
14.1.1.0 is directly connected, Ethernet0/0
R3#show ip route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
O
1.1.1.1 [110/175] via 23.1.1.2, 00:07:02, Serial2/0
2.0.0.0/32 is subnetted, 1 subnets
O
2.2.2.2 [110/65] via 23.1.1.2, 00:07:02, Serial2/0
3.0.0.0/24 is subnetted, 1 subnets
C
3.3.3.0 is directly connected, Loopback0
4.0.0.0/32 is subnetted, 1 subnets
O
4.4.4.4 [110/185] via 23.1.1.2, 00:07:02, Serial2/0
23.0.0.0/24 is subnetted, 1 subnets
C
23.1.1.0 is directly connected, Serial2/0
12.0.0.0/24 is subnetted, 1 subnets
O
12.1.1.0 [110/174] via 23.1.1.2, 00:07:02, Serial2/0
14.0.0.0/24 is subnetted, 1 subnets
O
14.1.1.0 [110/184] via 23.1.1.2, 00:07:03, Serial2/0
