OSPF message details - LSA overview

Catalog

One 、OSPF Message details ：

（1）———OSPF Head analysis ：

（2）———hello Field analysis ：

Two 、LSA message —— Link status notification

（1）——— brief introduction ：

（2）——— Header information :

（3）——— Data section :

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One 、OSPF Message details ：

——【{ Second layer frame header }+{IP Head }+【{OSPF Head ]+{OSPF data }】
----【224.0.0.0~~224.0.0.255】 These are multicast addresses , Of these multicast addresses TTL All for 1
----hello message : Build and maintain OSPF Neighbor's , formation OSPF Neighborhood watch ; Purpose IP Address :224.0.0.5
----IP Inside the head : Purpose IP The address is 224.0.0.5,IP The priority defaults to 6;TTL The default is 1; Agreement No :89

（1）———OSPF Head analysis ：

——version: 2---IPV4 Under the OPSF   3---ipv6 Under the OSPF
——message type: 1--hello   2--LSDBD    3---LSR     4--LSU      5--LSACK

——packet length: Packet size
——source OSPF router:. The sender's RID 【OSPF Between neighbors RID identical ,OSPF Neighbors can't get up 】

——area id: The area of the sender interface ID【 Direct link , Area ID atypism （ Two regions ）,OSPF Neighbors can't get up 】

——packet check: Parity check
——auth type: 0-- No certification 1-- Plaintext Authentication ﹑2--MD5 authentication 【 Authentication type and key are inconsistent ,OSPF Neighbors can't get up 】

——auth data: What is stored is the authentication information

（2）———hello Field analysis ：

—— Interface mask ; Interface IP The mask of the address 【 At the Ethernet interface , Masks between direct links are inconsistent OSPF Neighbors can't get up 】

——hello Sending interval :10/30 【10—— The radio type ,30——NBMA type ,hello The sending interval is inconsistent with the death timeout OSPF Neighbors can't get up 】
—— optional :DN  O  DC  L  NP  MC  E  MT
—— Interface priority :1  If you need to choose DR and BDR, But the interface priority is 0, Neighbors can't get up

——hello The time of death :40/120
——DR The address of :
——BDR The address of :

—— neighbor ID:
—— Their own RID:

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Two 、LSA message —— Link status notification

（1）——— brief introduction ：

Describe which interfaces are enabled OSPF, This interface's OSPF Link type , Network segment and mask , cost Value and so on ;【 You can understand LSA It is a routing representative 】

LSA It represents a router routing entry , But this route entry is represented in the form of a database .

LSA Refresh time : This LSA Who produced , Who is responsible for every 30 Minutes for this LSA Regenerate an update ;

LSA Aging time : LSA The maximum storage time in the database ,1 Hours , Subtract... Every second 1, If you can't get a refresh in an hour , Aging time becomes 0, This LSA It will be deleted from the database and flooded , Inform others OSPF Neighbors delete this aging LSA【 Routing changes 】

LSA Update conditions :   1、 Every time 30 Minutes to refresh    2、 When my router is running OSPF The interface of has changed , It will also trigger incremental updates ,LSA Your serial number will +1（ The interface has just been enabled OSPF Sometimes ）, This is the latest LSA.
LSA Part of the （ Every LSA They all have the same LSA Header information ）:

（2）——— Header information :

——LS age : Aging time 【1800 second （30 minute ）~~~3600 second （ An hour ）】, among 1800 It's cyclical LSA Refresh time ,3600 yes LSA Maximum aging time

——Options : optional DN O  DC  L  NP  MC  E  MT
——LS Type : What we are talking about is how many kinds of data are LSA
——Link State ID : Link state ID, It's a variable , According to LSA type , The values in this place are also different
——Advertising Router : Notification routing , This LSA Who made it , Just take this router RID Written here
——LS Seq Number : LSA The serial number of , Use this serial number to determine whose LSA Is the latest ,LSA Every update , Serial number +1

——Checksum : Parity sum , Used to verify the integrity of data transmission
——Length : It contains the total length of header information and data part
——Number of Links : Several interfaces of my router are enabled OSPF

（3）——— Data section :

LSA-1,LSA-2,  LSA-3,LSA-4,LSA-5,LSA-7

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Five basic data packages ：

HELLO	The neighbor's discovery 、 establish 、 Keep alive
LSDBD	Database description package – Database directory information
LSR	Link status request
LSU	Link status update — Carry all kinds LSA
LSACK	Link status confirmation

The above is only a personal point of view , If there is a mistake , Also please indicate ！ Feel free to leave a comment ！