11.5.OSPF

Dynamic routing protocol

OSPF : Open shortest path first protocol .
edition ：OSPFV2-IPV4 OSPFV3–IPv6
Update the way ： Trigger update , Existence period 30min
OSPF The network needs structured deployment ：
1. Zoning ,2 IP Address planning .
Distance vector characteristics of link state protocols ：----
- Transfer topology within the region . Transfer topology between regions .
cost value = Reference bandwidth / Interface bandwidth .
2)ospf Data packets
hello package , It is used to discover, establish and keep the neighborhood relationship alive , There is only Router—ID Used for router to pass router identity .
DD package , Database Description Database description package .
LSR package , Link status confirmation
LSU package Link status update
LSACK Link state
3）OSPF State machine
down： Agreement not started . Send after startup hello package , Enter the next state immediately .
init： Waiting for the neighbor to reply , If you carry the received hello package , Enter the next state together .
2-WAY Indicates that the neighbor relationship has been established ,
Matching conditions ： If successful , Go to the next state , If it fails , Keep alive only hello package .
Exstart: Pre start , Using fake DD Message comparison RID, Dayou enters the next state .
looding Use LAS /LSU/LSAK/ Get unknown path topology or route .
Full Neighborhood building , Convergence complete .
4）ospf Basic configuration
ospf1 router-id 1.1.1.1// Boot protocol , And configure the process number , At the same time, you can choose to configure , If you do not configure your choice .
Declare 1. Activate interface ,2 Publish topology or route .
Network Declare ,172.16.1.0. 0.0.0.255/0.0.0.0.
Unmask
Unmask ：32 Bit binary , Use dotted decimal to express , Continuous 0 And continuous 1 constitute , If the unmask is 0, Express IP The corresponding bit is fixed ： if 1, Indicates variable bit .
Pre: priority ; Range 0—255 Static default 60, The smaller the number is. , The more credible ,
OSPF The priority of is 10,
OSPF Route selection rules ： If there are multiple paths to a certain target , The whole interface is preferred COST Minimum value .
6**） Become the condition of adjacency **;
There can only be two nodes in the network from point to point .------- String line
MAC ( Multiple access ,） No nodes are set in a network .
If it is a point-to-point network type , Then it directly changes from neighbor relationship to neighbor relationship .
MAC Select the network type first DR/BDR role , De duplication update selection time 40 second , Others are not Orther
DR And drother Adjacency relations
BDR And drother Adjacency relations ,
DR And DR No neighbors
Priority election rules ,
1. Interface priority , The default priority is 1
2. DR/BDR Elections are non preemptive .
3. You can control the election by modifying the priority of the interface of the device participating in the election .