今天要讲的CCNP知识是关于ospf的。ospf首先发送hello包建立邻居，然后交换拓扑数据库，最后根据拓扑数据库计算出最佳路由然后放入路由表中。而拓扑数据库包含LSA,LSA最主要的有以下几类。 而今天涉及到的LSA类型包括1、2、3、5和7类LSA 。
末节区域：末节区域内的路由器不通告5类LSA,也就是说如果启用了末节区域重分发路由就不会起作用。但是可以用nssa末节区域末节区域。它使用7类LSA提供了像5类lsa那样的功能，这使得重分发路由还是能够起作用。有4种类型的末节区域。末节区域，绝对末节区域，nssa和绝对nssa。所有的末节区域都5类LSA通告到区域，绝对末节区域和绝对nssa连3类LSA也不通告，这使得路由表更小，而路由器处理路由使用的内存和cpu资源也更少。注意，配置为末节区域的区域内所有路由器都必须被配置为末节路由器，否者邻居关系将不能够正常建立。 网络拓扑图如下，采用6个思科路由器来组网：
全部配置如下： r1:
in e0/0 ip add 192.168.1.1 255.255.255.0 no sh ip ospf 1 a 0 r2: in e0/1 ip add 192.168.1.2 255.255.255.0 no sh ip ospf 1 a 0 in e0/0 ip add 192.168.2.1 255.255.255.0 no sh ip ospf 1 a 0 r3: in e0/1 ip add 192.168.2.2 255.255.255.0 no sh ip ospf 1 a 0 in e0/0 ip add 192.168.3.1 255.255.255.0 no sh ip ospf 1 a 1 router ospf 1 area 1 nssa r4: in e0/1 ip add 192.168.4.1 255.255.255.0 no sh ip ospf 1 a 1 in e0/2 ip add 192.168.5.1 255.255.255.0 no sh ip ospf 1 a 1 in e0/1 ip add 192.168.4.1 255.255.255.0 no sh router eigrp 1 net 192.168.4.0 redistribute ospf 1 metric 1000 100 255 1 1500 router ospf 1 redistribute eigrp 1 subnets metric 25 metric-type 1 area 1 nssa r5: in e0/1 ip add 192.168.4.2 255.255.255.0 no sh in loop 1 ip add 172.16.0.1 255.255.255.0 router eigrp 1 net 192.168.4.0 no au net 172.16.0.0 0.0.0.255 r6: in e0/0 ip add 192.168.5.2 255.255.255.0 http://www.luyouqiwang.com/14445/ no sh router ospf 1 net 192.168.5.2 0.0.0.0 a 1 area 1 nssa 验证命令： show ip ro show ip ospf nei show ip ospf data 先看看没有配置为nssa以前r3上show ip ospf data的输出 R3#show ip ospf data OSPF Router with ID (192.168.2.2) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 192.168.1.1 192.168.1.1 175 0x80000004 0x0091E7 1 192.168.1.2 192.168.1.2 84 0x80000006 0x002A58 2 192.168.2.2 192.168.2.2 63 0x80000007 0x0090DD 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.1.1 192.168.1.1 175 0x80000003 0x00B2D6 192.168.2.1 192.168.1.2 84 0x80000003 0x00B8CC Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.3.0 192.168.2.2 63 0x80000003 0x00F066 192.168.5.0 192.168.2.2 86 0x80000001 0x00430A Summary ASB Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.3.2 192.168.2.2 86 0x80000001 0x00D283 Router Link States (Area 1)(1类LSA) Link ID ADV Router Age Seq# Checksum Link count 192.168.2.2 192.168.2.2 66 0x8000000A 0x009CCC 1 192.168.3.2 192.168.3.2 101 0x8000000C 0x00BEAB 2 192.168.5.2 192.168.5.2 123 0x80000007 0x00A3BE 1 Net Link States (Area 1)(2类LSA) Link ID ADV Router Age Seq# Checksum 192.168.3.2 192.168.3.2 96 0x80000004 0x00A5D8 192.168.5.2 192.168.5.2 118 0x80000004 0x00A0D6 Summary Net Link States (Area 1)(3类LSA) Link ID ADV Router Age Seq# Checksum 192.168.1.0 192.168.2.2 66 0x80000005 0x0067E5 192.168.2.0 192.168.2.2 66 0x80000005 0x00F75E Type-5 AS External Link States(5类LSA) Link ID ADV Router Age Seq# Checksum Tag 172.16.0.0 192.168.3.2 182 0x80000001 0x00E30D 0 192.168.4.0 192.168.3.2 187 0x80000001 0x008BB4 0 发现其中有5类LSA。 r3路由表： R3#show ip ro Codes: C - connected, S - static, 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 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 172.16.0.0/24 is subnetted, 1 subnets O E1 172.16.0.0 [110/35] via 192.168.3.2, 00:06:09, Ethernet0/0 O E1 192.168.4.0/24 [110/35] via 192.168.3.2, 00:06:09, Ethernet0/0 O 192.168.5.0/24 [110/20] via 192.168.3.2, 00:06:09, Ethernet0/0 O 192.168.1.0/24 [110/20] via 192.168.2.1, 00:06:19, Ethernet0/1 C 192.168.2.0/24 is directly connected, Ethernet0/1 C 192.168.3.0/24 is directly connected, Ethernet0/0 其中有从eigrp分发到ospf中的两条外部路由。 r3上的邻居关系： R3#show ip ospf nei Neighbor ID Pri State Dead Time Address Interfa 192.168.1.2 1 FULL/DR 00:00:33 192.168.2.1 Etherne 192.168.3.2 1 FULL/DR 00:00:39 192.168.3.2 Etherne 只在1台路由器上配置为nssa，发现邻居关系断掉了。 R3(config)#router ospf 1 R3(config-router)#area 1 nssa R3(config-router)# *Mar 1 01:20:09.535: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.3.2 on Ethernet0/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset R3(config-router)#do show ip ospf nei Neighbor ID Pri State Dead Time Address Interface 192.168.1.2 1 FULL/DR 00:00:37 192.168.2.1 Ethernet0/1 192.168.3.2 1 DOWN/DROTHER - 192.168.3.2 Ethernet0/0 从show ip ospf nei中发现邻居192.168.3.2已经为DOWN状态了。现在我在r6和r4上也启用 nssa。 再看r3的邻居关系，发现已经恢复同192.168.3.2的邻居关系了。 R3# *Mar 1 01:21:18.071: %SYS-5-CONFIG_I: Configured from console by console R3# *Mar 1 01:23:37.351: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.3.2 on Ethernet0/0 from LOADING to FULL, Loading Done R3#show ip ospf nei Neighbor ID Pri State Dead Time Address Interface 192.168.1.2 1 FULL/DR 00:00:30 192.168.2.1 Ethernet0/1 192.168.3.2 1 FULL/DR 00:00:37 192.168.3.2 Ethernet0/0 再看拓扑数据库，发现5类LSA已经没有了，但是多出了7类LSA. R3#show ip ospf data OSPF Router with ID (192.168.2.2) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 192.168.1.1 192.168.1.1 904 0x80000004 0x0091E7 1 192.168.1.2 192.168.1.2 813 0x80000006 0x002A58 2 192.168.2.2 192.168.2.2 304 0x80000008 0x0094D6 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.1.1 192.168.1.1 904 0x80000003 0x00B2D6 192.168.2.1 192.168.1.2 813 0x80000003 0x00B8CC Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.3.0 192.168.2.2 792 0x80000003 0x00F066 192.168.5.0 192.168.2.2 92 0x80000001 0x00430A Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 192.168.2.2 192.168.2.2 96 0x8000000C 0x00441B 1 192.168.3.2 192.168.3.2 82 0x80000010 0x005C04 2 192.168.5.2 192.168.5.2 82 0x80000009 0x004515 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 192.168.3.2 192.168.3.2 95 0x80000006 0x00472F 192.168.5.2 192.168.5.2 82 0x80000006 0x00422D Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 192.168.1.0 192.168.2.2 307 0x80000006 0x000B3B 192.168.2.0 192.168.2.2 307 0x80000006 0x009BB3 Type-7 AS External Link States (Area 1) Link ID ADV Router Age Seq# Checksum Tag 172.16.0.0 192.168.3.2 104 0x80000001 0x00CEA8 0 192.168.4.0 192.168.3.2 104 0x80000001 0x007650 0 Type-5 AS External Link States（这个5类应该是区域0的） Link ID ADV Router Age Seq# Checksum Tag 172.16.0.0 192.168.2.2 95 0x80000001 0x006A18 0 192.168.4.0 192.168.2.2 162 0x80000001 0x0012BF 0 再看路由表： R3#show ip ro Codes: C - connected, S - static, 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 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 172.16.0.0/24 is subnetted, 1 subnets O N1 172.16.0.0 [110/45] via 192.168.3.2, 00:03:00, Ethernet0/0 O N1 192.168.4.0/24 [110/45] via 192.168.3.2, 00:03:00, Ethernet0/0 O 192.168.5.0/24 [110/20] via 192.168.3.2, 00:03:00, Ethernet0/0 O 192.168.1.0/24 [110/20] via 192.168.2.1, 00:06:46, Ethernet0/1 C 192.168.2.0/24 is directly connected, Ethernet0/1 C 192.168.3.0/24 is directly connected, Ethernet0/0 路由表中O后面多了个N1.N1路由为ospf nssa外部类型1.差不多就这样了。 顺便再配下绝对nssa。 r3： area 1 nssa no-summary 其余路由器上的配置还是相同，不必修改。 现在r3上拓扑数据库的输出 R3#show ip ospf data OSPF Router with ID (192.168.2.2) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 192.168.1.1 192.168.1.1 1666 0x80000004 0x0091E7 1 192.168.1.2 192.168.1.2 1575 0x80000006 0x002A58 2 192.168.2.2 192.168.2.2 1067 0x80000008 0x0094D6 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.1.1 192.168.1.1 1666 0x80000003 0x00B2D6 192.168.2.1 192.168.1.2 1575 0x80000003 0x00B8CC Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 192.168.3.0 192.168.2.2 1554 0x80000003 0x00F066 192.168.5.0 192.168.2.2 854 0x80000001 0x00430A Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 192.168.2.2 192.168.2.2 859 0x8000000C 0x00441B 1 192.168.3.2 192.168.3.2 844 0x80000010 0x005C04 2 192.168.5.2 192.168.5.2 844 0x80000009 0x004515 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 192.168.3.2 192.168.3.2 858 0x80000006 0x00472F 192.168.5.2 192.168.5.2 844 0x80000006 0x00422D Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 192.168.2.2 205 0x80000001 0x0013B5 Type-7 AS External Link States (Area 1) Link ID ADV Router Age Seq# Checksum Tag 172.16.0.0 192.168.3.2 867 0x80000001 0x00CEA8 0 192.168.4.0 192.168.3.2 867 0x80000001 0x007650 0 Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 172.16.0.0 192.168.2.2 856 0x80000001 0x006A18 0 192.168.4.0 192.168.2.2 858 0x80000001 0x0012BF 0 3类LSA现在只有一条link id为0.0.0.0的了，而原来的192.168.1.0和192.168.2.0已经不见了。 上面的CCNP知识确实有点复杂，要通过思科认证考试可不是那么简单的，大家需要课后慢慢体会。 |
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