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報告題目:OSPF 指導教授：陳明仕 報告者：黃元志 學號M
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internet 台灣的老鼠 大陸的大米
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router 不同網域的資料流，必需要透過 Router 來轉送彼此
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Routing table
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Real routing table Codes: C - connected, S - static, I - IGRP, 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, E - EGP i - IS-IS, 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 O E [110/1611] via , 00:09:46, GigabitEthernet2/2 O IA [110/511] via , 00:06:16, GigabitEthernet2/1 S [1/0] via /8 is variably subnetted, 23 subnets, 6 masks C /27 is directly connected, FastEthernet0/1
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Open Shortest Path First
routing protocol: link-state:ISIS、OSPF Distance vector:RIP、IGRP 屬於link-state ，負責傳遞routing table ，讓封包透過最短路徑傳送
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link-state database It has a map of every router, its links, and the state of the links. It also has a map of every network and every path to each network. There are same link-state database in every router
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Ospf packet format Hello DD(database descriptor )
LSR(link-state request) LSU(link-state update) LSAck(link-state Acknowledgment)
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Broadcast Multiaccess
OSPF Topologies Broadcast Multiaccess Point-to-Point NBMA X.25 Frame Relay
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Broadcast Multiaccess
DR BDR
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Electing the DR and BDR Hello packets exchanged via IP multicast DR
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* * * Neighborship Hello Router ID Neighbors Area-ID Router priority
C B Router ID *Hello(10)/dead intervals(40) Neighbors Area-ID Router priority DR IP address BDR IP address Authentication password Stub area flag afadjfjorqpoeru * Hello * *
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Discovering Routes DR E0 172.16.5.1 E0 172.16.5.3
Exstart State afadjfjorqpoeru I will start exchange because I have router ID Hello No, I will start exchange because I have a higher router ID. afadjfjorqpoeru Hello
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Discovering Routes DR E0 172.16.5.1 E0 172.16.5.3
Exstart State afadjfjorqpoeru I will start exchange because I have router ID Hello No, I will start exchange because I have a higher router ID. afadjfjorqpoeru Hello Exchange State afadjfjorqpoeru Here is a summary of my link-state database. DBD DBD afadjfjorqpoeru Here is a summary of my link-state database.
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Discovering Routes (cont.)
DR E0 E afadjfjorqpoeru afadjfjorqpoeru Thanks for the information! LSAck LSAck
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Discovering Routes (cont.)
DR E0 E afadjfjorqpoeru afadjfjorqpoeru Thanks for the information! LSAck LSAck Loading State afadjfjorqpoeru I need the complete entry for network /24. LSR afadjfjorqpoeru Here is the entry for network /24. LSU afadjfjorqpoeru LSAck Thanks for the information!
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Discovering Routes (cont.)
DR E0 E afadjfjorqpoeru afadjfjorqpoeru Thanks for the information! LSAck LSAck Loading State afadjfjorqpoeru I need the complete entry for network /24. LSR afadjfjorqpoeru Here is the entry for network /24. LSU afadjfjorqpoeru LSAck Thanks for the information! Full State
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Choosing Routes Cost=6 Cost=1 Cost=10 10.1.1.0/24 10.2.2.0/24
/24 A B C Cost=6 Cost=1 Cost=10 /24 Topology Table Net Cost Out Interface To0 To0 E0 This is the best route to
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OSPF Terminology Area 1 Area 0 Neighbors Cost = 10 Cost = 1785
Autonomous System Neighbors Interfaces Area 1 Cost = 10 Area 0 Cost = 1785 Cost = 6 Neighborship Database Lists Neighbors Topology Database Lists All Routes Routing Table Lists Best Routes
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Maintaining Routing Information
Link-State Change DR 1 x LSU B A Router A tells all OSPF DRs on
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Maintaining Routing Information
2 Link-State Change DR LSU 1 x LSU B A Router A tells all OSPF DRs on DR tells others on
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Maintaining Routing Information
2 Link-State Change DR LSU 1 x LSU 3 B A LSU Router A tells all OSPF DRs on DR tells others on
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Maintaining Routing Information
2 Link-State Change DR LSU I need to update my routing table. 4 1 x LSU 3 B A LSU Router A tells all OSPF DRs on DR tells others on
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Point-to-Point Neighborship
Router dynamically detects its neighboring router using the Hello protocol No election: Adjacency is automatic as soon as the two routers can communicate OSPF packets are always sent as multicast
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Configuring OSPF on Internal Routers
Broadcast Network Point-to-Point Network S0 E0 E0 S1 A B C <Output Omitted> interface Ethernet0 ip address ! interface Serial0 ip address router ospf 50 network area 0 network area 0 <Output Omitted> interface Ethernet0 ip address ! router ospf 1 network area 0 Can Assign Network or Interface Address.
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configuration router rip network 140.100.0.0
redistribute ospf 100 metric 3 router ospf 100 redistribute rip 100 metric 3
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Issues with Maintaining a Large OSPF Network
The SPF is running too often for me to route. I am only receiving LSAs, no data. OSPF OSPF OSPF OSPF My routing table is too big, I am running low on memory.
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The Solution: OSPF Hierarchical Routing
Area 0 Area 1 Area 2 Consists of areas and autonomous systems Minimizes routing update traffic Autonomous System
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OSPF Multi-Area Components
Routers LSAs Areas Internal afadjfjorqpoeru Area 0 I am a backbone. Type 1 afadjfjorqpoeru ABR Type 2 Area 1 I am standard. afadjfjorqpoeru ASBR Type 3/4 Area 2 I am a stub. afadjfjorqpoeru Type 5 Backbone
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Types of OSPF Routers Area 1 Backbone Area 0 Area 2
ABR and Backbone Router Backbone/ Internal Routers Internal Routers Internal Routers ASBR and Backbone Router ABR and Backbone Router External AS
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LSA
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type
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