OSPF - route aggregation [(summary) including configuration commands] ｜ address summary calculation method - detailed explanation

Catalog

One 、 Routing aggregation diagram ：

Two 、 Advantages of routing aggregation :

3、 ... and 、OSPF Inside, there is routing convergence , It can only be done in two places

（１）ABR: Only for routes in this region （ With O The first route ） Make a summary , Regional OＩA There is no way to summarize inter domain routes

　　　　—— To configure ：

（２）ASBR: Make route summary for the external routes redistributed

　　　　—— To configure ：

Four 、 Address summary calculation method ：

（１） ordinary , Summary of the same subnet ​

（２） complex , Summary of different subnets

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One 、 Routing aggregation diagram ：

Two 、 Advantages of routing aggregation :

• （１） Summarizing detailed routes can effectively reduce OSPF The database entry of the router is also the routing table entry , Reasonable saving of equipment performance
• （２） It can hide the routing shock caused by the instability of detailed routes
• （３） When doing route aggregation with two exits , There is one to do , Failure to do one will affect routing

3、 ... and 、OSPF Inside, there is routing convergence , It can only be done in two places

• （１）ABR: Only for routes in this region （ With O The first route ） Make a summary , Regional OＩA There is no way to summarize inter domain routes

• —— To configure ：

—— For regions 2 Summarize the intra domain routes 

ABR(config) #router os 100
ABR(config-router) #area　2 range 192.168.0.0 255.255.248.0
ABR(config-router) ＃exit

• （２）ASBR: Make route summary for the external routes redistributed

• —— To configure ：

ASBR(config)#router os 100
ASBR(config-router)#summary-address 172.16.0.0 255.255.248.0
ASBR(config-router) #exit

Four 、 Address summary calculation method ：

• （１） ordinary , Summary of the same subnet

    Judge which position has changed , Convert to binary 　, Keep the unchanged bits as the bits of the subnet mask = 16+5=21 You can also count the number of changes 24-3=21, All values of changed bits 0 Then the network address at this time is the summarized address
  192.168.00000000.0/21=192.168.0.0/21（255.255.248.0）

• （２） complex , Summary of different subnets

First of all, it is judged that the address bits of the paragraphs have changed , The following can be ignored , The main network number summarized into the address of this segment , Secondly, use the simple processing method above , After summary The subnet is 8+1=9 perhaps 16-7=9