课题内容：
CCNP实战之 OSPF转发地址研究
将area 2 配置为nssa区域，在R2上创建两个环回口，其中一个通告进OSPF，一个重分布进OSPF
观察七类LSA的情况；
在R1上做7转5时抑制转发地址，观察现象；
在R2上将RIP重分布进OSPF，观察 area 2 为特殊区域时和为普通区域时的现象；
拓扑：
配置基本的IP地址 （步骤省略）
每台设备的loopback接口地址为： 10.1.1.X/32 X = 设备编号
配置OSPF （步骤省略）
在R2上创建两个环回口，其中一个通告进OSPF，一个重分布进OSPF
R2#show run int l0
interface Loopback0
ip address 10.1.1.2 255.255.255.255
ip ospf 110 area 2
R2#show run int l1
Building configuration...
interface Loopback1
ip address 2.2.2.2 255.255.255.255
R2#show run | s r o
router ospf 110
area 2 nssa
redistribute connected subnets
观察七类LSA的情况
R2#show ip ospf database nssa-external
OSPF Router with ID (10.1.1.2) (Process ID 110)
Type-7 AS External Link States (Area 2)
LS age: 59
Options: (No TOS-capability, Type 7/5 translation, DC, Upward)
LS Type: AS External Link
Link State ID: 2.2.2.2 (External Network Number )
Advertising Router: 10.1.1.2
LS Seq Number: 80000001
Checksum: 0x254D
Length: 36
Network Mask: /32
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 20
Forward Address: 10.1.1.2
External Route Tag: 0
在R1上做7转5时抑制转发地址，观察现象
R1(config)#router ospf 110
R1(config-router)#area 2 nssa translate type7 always suppress-fa
R1#show ip ospf database external
OSPF Router with ID (10.1.1.1) (Process ID 110)
Type-5 AS External Link States
LS age: 18
Options: (No TOS-capability, DC, Upward)
LS Type: AS External Link
Link State ID: 2.2.2.2 (External Network Number )
Advertising Router: 10.1.1.1
LS Seq Number: 80000002
Checksum: 0x1A70
Length: 36
Network Mask: /32
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
// 应用了转发地址抑制参数，生成的五类LSA不再携带转发地址；//
在R2上将RIP重分布进OSPF
配置rip
R2#show run | s r r
router rip
version 2
network 124.0.0.0
no auto-summary
R4#show run | s r r
router rip
version 2
network 10.0.0.0
network 124.0.0.0
no auto-summary
验证：
R2#show ip route rip | begin Gateway
Gateway of last resort is not set
10.0.0.0/32 is subnetted, 2 subnets
R 10.1.1.4 [120/1] via 124.1.1.4, 00:00:03, Ethernet0/2
重分布：
R2(config)#router ospf 110
R2(config-router)#redistribute rip subnets metric-type 1
验证：
R2#show ip ospf database | begin Type-7
Type-7 AS External Link States (Area 2)
Link ID ADV Router Age Seq# Checksum Tag
2.2.2.2 10.1.1.2 520 0x80000001 0x00254D 0
10.1.1.4 10.1.1.2 53 0x80000001 0x004333 0
R3#show ip route ospf | begin Gateway
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
O E2 2.2.2.2 [110/20] via 13.1.1.1, 00:09:14, Serial1/1
10.0.0.0/32 is subnetted, 3 subnets
O IA 10.1.1.2 [110/75] via 13.1.1.1, 00:09:50, Serial1/1
O E1 10.1.1.4 [110/84] via 13.1.1.1, 00:01:33, Serial1/1
124.0.0.0/24 is subnetted, 1 subnets
O IA 124.1.1.0 [110/74] via 13.1.1.1, 00:10:30, Serial1/1
观察 area 2 为特殊区域时的现象
R2#show ip ospf database nssa-external 10.1.1.4
OSPF Router with ID (10.1.1.2) (Process ID 110)
Type-7 AS External Link States (Area 2)
LS age: 121
Options: (No TOS-capability, Type 7/5 translation, DC, Upward)
LS Type: AS External Link
Link State ID: 10.1.1.4 (External Network Number )
Advertising Router: 10.1.1.2
LS Seq Number: 80000001
Checksum: 0x4333
Length: 36
Network Mask: /32
Metric Type: 1 (Comparable directly to link state metric)
MTID: 0
Metric: 20
Forward Address: 124.1.1.4
External Route Tag: 0
为普通区域时的现象
将area 2修改为普通区域 （步骤省略）
观察LSA：
R1#show ip ospf database external
OSPF Router with ID (10.1.1.1) (Process ID 110)
Type-5 AS External Link States
Routing Bit Set on this LSA in topology Base with MTID 0
LS age: 28
Options: (No TOS-capability, DC, Upward)
LS Type: AS External Link
Link State ID: 2.2.2.2 (External Network Number )
Advertising Router: 10.1.1.2
LS Seq Number: 80000001
Checksum: 0x1674
Length: 36
Network Mask: /32
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
Routing Bit Set on this LSA in topology Base with MTID 0
LS age: 28
Options: (No TOS-capability, DC, Upward)
LS Type: AS External Link
Link State ID: 10.1.1.4 (External Network Number )
Advertising Router: 10.1.1.2
LS Seq Number: 80000001
Checksum: 0xD7A8
Length: 36
Network Mask: /32
Metric Type: 1 (Comparable directly to link state metric)
MTID: 0
Metric: 20
Forward Address: 124.1.1.4
External Route Tag: 0
来自R2环回口的网络，重分布进入OSPF之后，并没有携带转发地址；
R2上来自RIP的路由重分布进入OSPF之后携带了转发地址；
谢谢大家！
我是乾颐堂CCIE导师，CCIE培训金牌讲师达叔。
本博客由乾颐堂达叔独家冠名写出，素材来自乾颐堂日常工作及达叔和他身边的CCIE们的故事。