Summary of vlsm. CIDR and summary

CIDR is just an extension of aggregation ~ Is a special set! He generally summarizes the following!

/8/16/24 instead of/7/19/25!

172.16.0.0/16

172.17.0.0/16

172.18.0.0/16

172.19.0.0/16

These are four class B address blocks. When we merge them, we use 172.16.0. 0/14 to merge them. This is the CIDR!

For summary: This is just a feature. It is divided into automatic summary and manual summary. We have different routes.

The protocol supports different summary formats! For example, OSPF does not automatically summarize on the classification boundary ~

For example,

We can summarize and use

IP Summary-address subnet 1 10.1.0.0 255.255.255.0

For example, we can summarize (ABR) in OSPF)

Area 0 range 172.16.96.0 255.255.255.255.255.255.255.

Or (ASBR)

Summary-address 172.16.32.0 zookeeper

The summary on BGP is

Aggregate-address 10.1.0.0 255.255.0.0 Summary-only

The summary on Is-Is is

Summary-address 10.3.2.0 255.255.255.0 Level 1

Automatic summary is the boundary that can only be summarized to the class.

For example:

172.16.1.1/24

172.16.2.1/24

Automatic summary is summarized to 172.16.0.0/16

If you are manual, you are happy to summarize where it is, and where it is, just as needed!

For example, you can aggregate the data to 172.16.0.0/20 or 172.0.0.0/8.

For example, if the ISP gives tnt a 210.231.223.0/24 network, if it is hidden by default, it is/24, then there is only one network segment and there are only 254 addresses, then in a practical application, TNT only assigns addresses of 64 hosts to Qingdao Company, which must be divided into several segments. For example, if there are 60 hosts in Qingdao branch, you only need to allocate the address 210.231.223.64/255.255.255.192 to him, that is, listen-221.231.223.126, broadcast address 127, and then divide the 32 address quotas 210.231.223.128 of Jinan Branch and Tianjin branch into two subnets, 210.231.223.128/255.255.255.192, namely 210.231.223.128-158, broadcast 159, 210.231.223.159-190

Vlsm is often used to maximize the number of available addresses in a network.

For vlsm, the CIDR and summary are just vlsm applications! In our network scale, we can support different submasks!

Source: Internet