Basic knowledge of ospf
One OSPF (Open shortest path first)
① is based on IP, port number 89, multicast, no loop mechanism.
② link-state routing protocol Huasan: AD 10 Cisco: AD 110
③ COST (link cost) = 10 ^ 8 / interface bandwidth
The narrower the bandwidth of ④, the greater the cost.
Bandwidth is inversely proportional to cost
⑤ default priority: internal 10 external 150 static 60
⑥ cares about cost and bandwidth
2. OSPF message type
① Hello establish and maintain ospf and neighbor relationship (establish and maintain)
② DBD link-state database description information (summary)
③ LSR link-state request, requesting link-state information from ospf neighbors (reply)
④ LSU link-state update (request)
⑤ LSAck confirms (acknowledges) the LSA in LSU
Three OSPF three tables
① neighbor table
② topology table (lsdb link-state database)
③ routing tabl
4. The working process of OSPF protocol
Find neighbors, establish neighbor relationships, pass link-state information, calculate routes
Five OSPF network types
① broadcast supports multiple access to broadcast
② peer-to-peer (P2P)
③ point to multipoint (P2MP)
④ NBMA
Six DR BDR
① DR Master (specified route)
② BDR backup (backup specified route)
Note: when ospf elects a route, the cost value does not affect the election DR/BDR, it only affects the routing algorithm.
Election DR BDR rule: the higher the priority of the ① interface, the more priority it will be selected as DR.
② if the priority is the same, the bigger the router-id, the better the priority.
③ if the router does not set router-id, then choose the IP address of the interface, the larger the priority.
Optimization of Seven OSPF
① HELLO time
② BFD
③ spf1-100
④ interface type
Eight OSPF regions
Backbone area, non-backbone area, special area.
Nine wildcard mask: the common name for anti-mask
Ten small experiments OSPF
R1
R1 (config) # int s 0Universe 1
R1 (config-if) # ip add 192.168.12.1 255.255.255.0
R1 (config-if) # no shu
R1 (config-if) # exi
R1 (config) # router ospf 1
R1 (config-router) # network 192.168.12.0 0.0.255 area 0
R1#show ip route
R1#show ip ospf neighbor
R2
R2 (config) # int s 0Universe 0
R2 (config-if) # ip add 192.168.12.2 255.255.255.0
R2 (config-if) # no shu
R2 (config-if) # int s 0Universe 1
R2 (config-if) # ip add 192.168.23.2 255.255.255.0
R2 (config-if) # no shu
R2 (config) # router ospf 1
R2 (config-router) # network 192.168.12.0 0.0.255 area 0
R2 (config-router) # network 192.168.23.0 0.0.0.255 area 0
R2 (config-router) # net
R2 (config-router) # network
R2#show ip route
R2#show ip ospf neighbor
R3
R3 (config) # int s 0lap 0
R3 (config-if) # ip add 192.168.23.3 255.255.255.0
R3 (config-if) # no shu
R3 (config) # router ospf 1
R3 (config-router) # network 192.168.23.0 0.0.0.255 area 0
R3#show ip route
R3#show ip ospf neighbor
