OSPF 指令小記

1.Classless
2.Link-State Protocol
3.靠Hello Packets建鄰居關係，定時送Link-State Advertisement(LSA), LSA會丟給同一個Area的Router(要先建鄰居關係才會交換路由與RIP不同),每個Router會把收到LSA集合成Link State Database,並用SPF演算法算出最佳路徑

Hello Packets(Router ID(獨一無二),Hello and dead Intervals,Area ID,Authentication,Stub Area Flag.....)
Hello Packets每10秒丟一次


OSPF有3張Table
Adjacency Table (鄰居關係)
需要Hello And Dead Intervals,AreaID,Authentication,Stub Area Flag相同,鄰居關才才會建起來!


Topology Database(Link State Database)

     |
     |    (SPF演算法)
     |
    V

Routing Table(Forwarding Table)

OSPF不會定時會更新，只有Topology改變時，才會更新Routing Table


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Router ID
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預設為所有UP的介面，最大的IP
例如:

Router#show ip ospf
 Routing Process "ospf 168" with ID 10.2.2.2
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
 External flood list length 0
    Area BACKBONE(0) (Inactive)
        Number of interfaces in this area is 0
        Area has no authentication
        SPF algorithm executed 1 times
        Area ranges are
        Number of LSA 1. Checksum Sum 0x009dc7
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0


Router#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol

FastEthernet0/0        10.1.1.2        YES manual up                    down

FastEthernet0/1        10.2.2.2        YES manual up                    down

Vlan1                  unassigned      YES unset  administratively down down

( Protocol Down 的原因是我沒接網路線,如果要重設Router ID,要先把原本的OSPF no掉)



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假設有一Router有兩個介面
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FA 0   ==> IP  10.2.2.2/16
FA 1   ==> IP  10.1.1.2/16


B2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
B2(config)#router ospf 100   --->100為 Process ID (Process ID不同也不會影響鄰居關係的建立)
B2(config-router)#network 10.2.2.2 0.0.0.0 area 0  (在這個介面啟用OSPF)
B2(config-router)#network 10.1.1.2 0.0.0.0 area 0  (在這個介面啟用OSPF)


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如果有介面不想收送Routing Update，可以使用以下指令
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B2(config-router)#passive-interface serial 0/0/0




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Loopback (設完可以當OSPF的Router ID)
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B1(config)#interface loopback 0

%LINK-5-CHANGED: Interface Loopback0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up

B1(config-if)#ip address 1.1.1.1 255.255.255.0

(不用no shutdown)


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檢查指令
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show ip route
show ip protocol
show ip ospf
show ip ospf interface  (列出有哪些介面啟用OSPF)

show ip ospf neighbor



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啟用Load Balancing
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maximum-paths 6



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停用Load Balancing
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maximum-paths 1


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啟用驗證,在介面下(收送都做驗證)
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Core(config-if)#ip ospf authentication-key abc   (密碼為abc)
Core(config-if)#ip ospf authentication message-digest   (打完這行才有啟用,並且用MD5加密)


相關介紹請參考這裡