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OSPF

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zealot's version from 2017-02-01 19:26

Section

Question Answer
Characteristics of OSPFClassless, Efficient, Fast Convergence, Scalable, Secure
OSPF AD110
OSPF DatabasesAdjacency, Link State, Forwarding
OSPF MessagesHello, DBD, LSR, LSU, LSA
OSPF Link State Routing ProcessEstablish Adjacencies, Establish Link State Advertisements, Build Topology Table, Execute SPF Algorithm
OSPF Hello Packet Interval10 seconds
Dead IntervalPeriod router waits for Hello packet before declaring neighbor dead
Problems with Multiaccess NetworksMultiple Adjacencies and Flooding of LSA
Purpose of DRRouter that collects and distributes LSAs
After convergence when are LSUs sentChange in topology, every 30 minutes
How is router ID determined?Router command, highest loopback address int, highest int ip
When does router ID change?Router Reload, OSPF process cleared
Clear OSPF commandclear ip ospf process
Why is it good to use area ID 0 with single area OSPF?Makes it easier to support multiarea OSPF
What is OSPF cost?Accumulated value from one router to destination
What must be done to assist OSPF make the correct cost determination?Reference bandwidth must be changed for networks with higher than 100 mbs
When changing reference bandwidth where must it be changed?All routers on the OSPF network
Command to confirm adjancencies?show ip ospf neighbor
Why might OSPF not form an adjacency?Subnet masks do not match, OSPF hello or dead timers don't match, OSPF networks don't match, missing or incorrect OSPF command
What version of OSPF runs ipv6?OSPFv3
OSPF ImplementationsSingle Area - All routers in one backbone area, Multiarea - All areas connect to backbone area, routers connecting areas are ABR (Area Border Router)
Advantages of Hierarchical Topology for Multiarea OSPFSmaller routing tables, Reduced Link State overhead, Reduces SPF calculations
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