Network equipment hard core technology insider router Chapter 4 Jia Baoyu sleepwalking in Taixu Fantasy (Part 2)

Last time when it comes to , Twelve Jinchai learned the distance with other neighbors , As shown in the figure below ：

that , adopt RIP The shortest path calculated by the routing protocol , After adding the factor of distance between nodes , Is it still the shortest path ？

Let's first look at the simplest problem , Just look at Daiyu 、 Xiangyun 、 Yuanchun and Baochai are four nodes ：

In the figure , Xiangyun / Bao Chai / The distance from Yuanchun to Daiyu ( Link overhead ) Respectively 2,7,8. They respectively announced this information to the gold hairpins around them ：(LSA notice )

“ Bao Chai , I'm Xiangyun , The link cost from me to Daiyu is 2.”

After Baochai received this message , take 2 Add the link overhead between yourself and Xiangyun 5, obtain 7, And keep this information in your heart ： Through Xiangyun ( Next jump ), The cost of arriving at Daiyu is 7.(LSA Database establishment )

Soon , Each gold hairpin has produced its own LSA database ：

The gold hairpins each according to their own LSA database , Made the best choice for the path to Daiyu , As shown in the figure ：

At this time , Yuan Chun found , The cost of going to Daiyu through Xiangyun is 3, Compared with the cost of directly connecting Daiyu 8 smaller . Based on the principle of minimum total cost , Yuan Chun chose the path to Daiyu through Xiangyun .

meanwhile , Yuan Chun looks around ( Except for Xiangyun ), It will also be updated LSA： Go to Daiyu by yourself , The cost is 3.

After Baochai received this message , Found the fastest way to Daiyu ……

And so on , The nodes of the whole network can iteratively calculate the best route to Daiyu ：

It's easy to see , Baoyu can pass the Spring Festival 、 Li Wan 、 Xiangyun arrives at Daiyu , Is the nearest path .

Because the path obtained by the above algorithm is the shortest , therefore , This routing protocol is called OSPF (Open Shortest Path First).

We found that , adopt OSPF The optimal path obtained by the routing protocol , And RIP There are some differences in the optimal path obtained by routing protocols ：

RIP The optimal path obtained is 3 jump , and OSPF Need to go through 4 jump . however ,OSPF The total cost of the path is the smallest .

OSPF The algorithm used , It's a mathematician Dijkstra Invented , So it's also called Dijkstra Algorithm .

With Dijkstra Algorithm , Baoyu can be reunited with Daiyu , Read together 《 West Chamber 》 了 .

Baoyu said in Daiyu's ear ：“ You are the melancholy body , I'm the one who looks great ……”

Daiyu ：“ Bitch is shameless , You want to talk to caimoukun PK Do you ？”

Baoyu wakes up , I turned out to be Li Xiaoyao , Just now all this is a dream , Next to me is my aunt patting me awake ……

Today's question ： If a malicious attacker connects the attacking device to the network and sends OSPF LSA, Publishing should lead to other IP Routing of addresses , Interfere with the operation of routers in the network , How to avoid this attack ？

Answers to the questions left over yesterday ：

Baoyu can be in both spring greeting and spring cherishing 3 Jump to Daiyu , So which path will you choose ？

because RIP Support load balancing of equivalent paths , The router will follow a certain algorithm , Send packets evenly to the two links .