Detailed explanation of OSPF LSA of routing Foundation

OSPF LSA A detailed overview of

Principle overview ：

OSPF It is a dynamic routing protocol based on link state , Each station OSPF The router will generate relevant LSA, And these LSA Announce it . Router received LSA after , They will be stored in the link state database LSDB in .

LSA There are many different types , Different types of LSA The functions and functions of are different , Here are a few common ones LSA：

Type-1 LSA(Router LSA)： Every router generates , It is used to describe the direct link state and overhead value of the router .Type-1 LSA Only flood within the area , No flooding to other areas .

Type-2 LSA(Network LSA)： It is DR Produced , Mainly used to describe the DR The network mask of the network segment and the routers in the network segment .Type-2 LSA Only flood within the area , No flooding to other areas .

Type-3 LSA(Network Summary LSA); It is from ABR(Area Boundary Router) Produced ,ABR The router will the connected area Type-1 and Type-2 LSA Convert to Type-3 LSA, Used to describe the routing information between regions .Type-3 LSA Can flood the whole AS(Autonomous System, Autonomous Region ) Inside , But it can't flood to Totally Stub Areas and Totally NSSA(Not-So-Stubby Area) Area .

Type-4 LSA(ASBR Summary LSA); It is from ASBR(Autonomous System Boundary Router) In the area ABR Produced , Used to describe ASBR The routing .Type-4LSA Can flood the whole AS Inside , But it can't flood to Stub Area 、Totally Stub Area 、NSSA Areas and Totally NSSA In the region .

Type-5 LSA(AS External LSA)： It is from ASBR Produced , Used to describe AS Routing of external networks .Type-5 LSA Can flood the whole AS Inside , But it can't flood to Stub Area 、Totally Stub Area 、NSSA Areas and Totally NSSA In the region .

Type-6 LSA(Group Membership LSA)： stay MOSPF It is used to identify the user multicast route used by multicast group members in .

Type-7 LSA(NSSA LSA)： It is from NSSA Regional or Totally NSSA Regional NSSA ASBR Produced , Used to describe AS External routing .Type-7 LSA Can only appear in the NSSA Regional or Totally NSSA Inside the area .

Type：

In the display information ,Type According to the LSA The type of , This means Router LSA. Different types of LSA The function of is different from the scope of flood area .Router LSA Describes the direct link or interface of the router , The flood scope is the interior of the area , So that other routers in the region can understand the status information of their direct link or interface ;

Meaning of other parameters ：

Ls id：

about Router LSA,Ls id Is to produce the Router LSA Of routers Router-ID.

Adv rtr：

Adv rtr It describes LSA Which router generated it . about Router LSA Speaking of ,Adv rtr Is to produce the Router LSA Of routers Router-ID.

Seq#：

This article LSA Will maintain a Seq#( Serial number ), It's this one LSA Your router will pass by default 30s Periodic flooding of this LSA, Every flood , Add... To the serial number 1,LSA The larger the serial number , Show this LSA New .

Chksum：

chksum( The checksum ) Used to verify LSA The integrity of . be-all LSA Will be saved in the router LSDB in , Every time 5min The accountant calculates once . If the router receives the same message LSA, And the serial number is the same , Their checksums are compared , The larger the checksum, the corresponding LSA New .

Ls age：

Ls age Refer to LSA Aging time , Used to represent LSA How long have you lived , The maximum value is 3600s. When a router generates a LSA When , The router will LSA The aging time of is set to 0.LSA After production , Whether it's staying in the router LSDB Inside , Still in the process of transmission , Aging time will continue to increase , In order to prevent LSA Routing feedback caused by the expiration of , The router will every 30min Flooding itself LSA. If the comparison between serial number and checksum cannot determine the latest LSA when , It will compare the aging time .

stay LSDB in , If the aging time difference is greater than 15min above , be Ls age The smaller the value of , explain LSA New , If there is a difference 15min Inside , Think of two LSA It's the same .

In the information displayed above ,Link count The above parameter information is usually called LSA Header information ,Link count And the following parts are specific link description information ,Link count Marked this LSA Number of link information described . about P-2-P Link type ,Link ID It refers to the neighbor interface on the chain IP Address ; about TranNet Link type ,Link ID Refer to DR Interface IP Address .Data Refers to the of its own interface IP Address ,Link Type Refers to the link type of the interface ,Metric It refers to the time when the router reaches the link itself Cost value , It should be noted that ,OSPF The agreement will put Broadcast and NBMA Both networks with multiple access capability are considered to be TransNet The Internet .

The experiment purpose ：

understand OSPF Different types of LSA The role of

be familiar with OSPF Different types of LSA Flood range of

be familiar with LSA Meaning of important fields in

The topology ：

Basic configuration ：

R1：

Log in and copy

      
      

       
       #
       
       
interface GigabitEthernet0/0/0
       
       
 ip address 10.1.234.1 255.255.255.0 
       
       
#
       
       
interface GigabitEthernet0/0/1
       
       
#
       
       
interface NULL0
       
       
#
       
       
interface LoopBack0
       
       
 ip address 10.0.1.1 255.255.255.0 
       
       
 ospf network-type broadcast
       
       
#
       
       
ospf 1 router-id 10.0.1.1 
       
       
 area 0.0.0.0 
       
       
 network 10.1.234.1 0.0.0.0 
       
       
 area 0.0.0.2 
       
       
 network 10.0.1.1 0.0.0.0
      
      
      
      

       
       
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R2：

Log in and copy

      
      

       
       #
       
       
interface GigabitEthernet0/0/0
       
       
 ip address 10.1.234.2 255.255.255.0 
       
       
 ospf dr-priority 254
       
       
#
       
       
interface GigabitEthernet0/0/1
       
       
#
       
       
interface NULL0
       
       
#
       
       
interface LoopBack0
       
       
 ip address 10.0.2.2 255.255.255.0 
       
       
 ospf network-type broadcast
       
       
#
       
       
ospf 1 router-id 10.0.2.2 
       
       
 area 0.0.0.0 
       
       
 network 10.0.2.2 0.0.0.0 
       
       
 network 10.1.234.2 0.0.0.0
      
      
      
      

       
       
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R3:

Log in and copy

      
      

       
       #
       
       
interface GigabitEthernet0/0/0
       
       
 ip address 10.1.234.3 255.255.255.0 
       
       
 ospf dr-priority 255
       
       
#
       
       
interface GigabitEthernet0/0/1
       
       
#
       
       
interface NULL0
       
       
#
       
       
interface LoopBack0
       
       
 ip address 10.0.3.3 255.255.255.0 
       
       
 ospf network-type broadcast
       
       
#
       
       
ospf 1 router-id 10.0.3.3 
       
       
 area 0.0.0.0 
       
       
 network 10.0.3.3 0.0.0.0 
       
       
 network 10.1.234.3 0.0.0.0 
       
       
 area 0.0.0.1 
       
       
 network 10.0.35.3 0.0.0.0
      
      
      
      

       
       
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R4：

Log in and copy

      
      

       
       #
       
       
interface GigabitEthernet0/0/0
       
       
 ip address 10.1.234.4 255.255.255.0 
       
       
 ospf dr-priority 0
       
       
#
       
       
interface GigabitEthernet0/0/1
       
       
#
       
       
interface NULL0
       
       
#
       
       
interface LoopBack0
       
       
 ip address 10.0.4.4 255.255.255.0 
       
       
 ospf network-type broadcast
       
       
#
       
       
ospf 1 router-id 10.0.4.4 
       
       
 area 0.0.0.0 
       
       
 network 10.0.4.4 0.0.0.0 
       
       
 network 10.1.234.4 0.0.0.0
      
      
      
      

       
       
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R5:

Log in and copy

      
      

       
       #
       
       
interface Serial2/0/0
       
       
 link-protocol ppp
       
       
 ip address 10.0.35.5 255.255.255.0 
       
       
#
       
       
interface Serial2/0/1
       
       
 link-protocol ppp
       
       
#
       
       
interface GigabitEthernet0/0/0
       
       
#
       
       
interface GigabitEthernet0/0/1
       
       
#
       
       
interface NULL0
       
       
#
       
       
interface LoopBack0
       
       
 ip address 10.0.5.5 255.255.255.0 
       
       
#
       
       
ospf 1 router-id 10.0.5.5 
       
       
 import-route direct
       
       
 area 0.0.0.1 
       
       
 network 10.0.35.5 0.0.0.0
      
      
      
      

       
       
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Check your router's LSDB：

R1：

R2:

R3：

R4:

R5:

1 class Lsa：

(1) It mainly describes the link information of the direct interface with the route ;

(2) Each router will generate one 1 class Lsa entry ;

(3)1 class Lsa There are four types of , Respectively p2p、stubnet、transnet、virtual;

1. Lsa The meaning of internal elements :

The explanation of each parameter ：

type： Express Lsa The type of ,router Express 1 class Lsa;

Ls id： It means that we should lsa The name of ;

adv rtr： Indicates that the lsa The router ;

Ls age： Indicates aging time , For the initial 0,3600 For aging ;

Len： Express Lsa Message length ;

seq： Serial number , For comparison Lsa New and old ;

Checksum： The checksum

Link count： The amount of link information

Link id： Information representing the pseudo node

Data： Indicates that it is connected to the pseudo node IP

link type： describe 1 class Lsa The type of ,transnet Expressed as broadcast or NBMA type

Metric： Cost value

2 class Lsa：

(1) Mainly on the radio or NBMA In the network type , Information used to describe pseudo nodes ;

(2)Lsa The internal elements are shown in the figure below ：

type： Express lsa type ,network Expressed as 2 class Lsa;

Attached router： Indicates neighbor routing

3 class Lsa：

(1) It's mainly about... In different areas 1 class Lsa and 2 class Lsa convert , So that it can be transmitted in different areas .

(2) Only ABR Route can be converted , And 3 class Lsa Flooding in this area .

(3)3 class Lsa The meaning of each element ：

End of experiment ;

remarks ： If there is a mistake , Please understand ！

This article is my study notes , For reference only ！ If there is a repetition ！！！ Please contact me