OSPF-LSA系列—LSA TYPE 3

通用属性：
类型TYPE、Link ID、ADV Router三者标示了LSA的唯一性


Age存在时间，最大为3600s，正常情况下不会超过1800s，30min周期更新，3600s没有更新会删掉LSA
Seq number范围是80000001-7FFFFFFF
Checksum说明LSA在传输过程有没有出现错误
Age、Seq number和Checksum三者标示了LSA的新旧程度
当多份LSA来到设备时会比较Age、Seq number和Checksum三者来选取一份放入LSDB表中
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通告者：本区域ABR的router-id
传播范围：在区域间传播
内容：路由（网络号、掩码和开销）
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ABR定义：设备至少有一个接口和area 0相连，还有其它接口和其它区域相连，并且和area 0相连的OSPF邻居到达FULL状态。
注意：ABR不能接收从非骨干区域传递过来的TYPE 3类路由（LSA存在，但是不能加入到路由表中）


在TYPE 3转TYPE 3的时候，如果本地（ABR）存在一条比转换的TYPE 3路由更优的话，该TYPE 3转TYPE 3不会执行


R3#show ip route 


     1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
O IA    1.1.1.1/32 [110/75] via 23.1.1.2, 00:13:02, Serial1/0     
   
R3(config)#ip route 1.1.1.1 255.255.255.255 23.1.1.2   设置一条更优的路径


R3#show ip route 


     1.0.0.0/32 is subnetted, 1 subnets
S       1.1.1.1 [1/0] via 23.1.1.2


R4#debug ip routing   
R4#
*Mar  1 00:18:38.363: RT: del 1.1.1.1/32 via 34.1.1.3, ospf metric [110/85]
*Mar  1 00:18:38.367: RT: delete subnet route to 1.1.1.1/32
*Mar  1 00:18:38.367: RT: NET-RED 1.1.1.1/32
*Mar  1 00:18:38.367: RT: delete network route to 1.0.0.0
*Mar  1 00:18:38.371: RT: NET-RED 1.0.0.0/8
R4#
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R4#show ip ospf database 


            OSPF Router with ID (0.0.0.4) (Process ID 100)


                Summary Net Link States (Area 10)


Link ID         ADV Router      Age         Seq#       Checksum
2.2.2.2         0.0.0.3         331         0x80000001 0x00A749
3.3.3.3         0.0.0.3         341         0x80000001 0x00F636
12.1.1.0        0.0.0.3         325         0x80000002 0x00A838
23.1.1.0        0.0.0.3         341         0x80000001 0x00B62A
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R4#show ip ospf database summary 


            OSPF Router with ID (0.0.0.4) (Process ID 100)


                Summary Net Link States (Area 10)


  Routing Bit Set on this LSA
  LS age: 288
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 2.2.2.2 (summary Network Number)
  Advertising Router: 0.0.0.3
  LS Seq Number: 80000001
  Checksum: 0xA749
  Length: 28
  Network Mask: /32
        TOS: 0  Metric: 65 


  Routing Bit Set on this LSA
  LS age: 298
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 3.3.3.3 (summary Network Number)
  Advertising Router: 0.0.0.3
  LS Seq Number: 80000001
  Checksum: 0xF636
  Length: 28
  Network Mask: /32
        TOS: 0  Metric: 1 


  Routing Bit Set on this LSA
  LS age: 285
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 12.1.1.0 (summary Network Number)
  Advertising Router: 0.0.0.3
  LS Seq Number: 80000002
  Checksum: 0xA838
  Length: 28
  Network Mask: /24
        TOS: 0  Metric: 74 


  Routing Bit Set on this LSA
  LS age: 308
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 23.1.1.0 (summary Network Number)
  Advertising Router: 0.0.0.3
  LS Seq Number: 80000001
  Checksum: 0xB62A
  Length: 28
  Network Mask: /24
        TOS: 0  Metric: 64 
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将AGE置为3600s时，说明要删除这条路由