OSPF knowledges

Attributes:
Type : link-State
Algorithm : Dijkstra
Metric : Cost
AD :100
protocoll / Transport : IP / IP/89
Authentication : plain , MD5
ALLSPF : 224.0.0.5
ALLDR : 224.0.0.6

Neighbor requirements:
-Interface primary ip address must be in same subnet
-Must not be passive on the connected interface
-Hello / Dead interval timer must match
-RouterID’s must be unique
-Ip MTU must match
-Must pass neighbor authentication

Hello / Dead Timers:
nonbroadcast/ multipoint broadcast / multipoint nonbroadcast : 30/120
broadcast / point-to-point : 10/40

Topologies:
nonbroadcast / broadcast : full mesh
point-to-point :

Area types:
standard
Stub areas: type5 lsa-s relpaced with default routes
tottaly stubby areas type 3,4,5 lsa-s replaced with default routes
NSSA: Type 5 LSA-s converted to type 7 within the area

External route types:
E1: cost of the advertising ASBR + external cost of the route
E2: cost of the route as seen by the ASBR

Troubleshooting:
show ip ospf interface
show ip ospf neighbor(s) kivonat
-neighbors
-priority
-State
-Dead time
-Address
-Interface

debug ip ospf

Speedup ospf:
-Each area including backbone, should contain no more than 50 routers
-Area and domain summarization
-Hub-and-spoke design ( stub and nssa areas )
– ( single interface at the hub with broadcast / point-to-multipoint network )
– ( individual point-to-point to each spoke )
-Area filtering
-Flooding reduction ( elimitane the periodic refresh of unchanged LSAs )
– Helyette a következők teendőek:
— reducing the number of routers in an area
— reducing the nomber of adjacenties for stressed routers
— use more hierachie
-Fast convergence ( subsecund timers for ospf )
-Incremental SFP ( nem a teljes fát számolja újra, csak a hibás részt )
-Bidirectional forwarding detection ( layer 2 link hellos to detect the dead / half dead links )