Detailed explanation of OSPF five LSA types

Experimental topology:

**

Brief description:

**

cisco and Huawei have different management distances and configurations

CISCO:110				HUAWEI:10

The route learned by Huawei through ospf is an internal router, with a value of 10,
If rip route and external router are introduced into ospf process, 150

ospf is acyclic inside, but of course, it can't be acyclic. Acyclic is impossible. Acyclic is so fun, isn't it? It may be acyclic when republishing.

Premise:
Each router has been configured with OSPF, and the loopback interface 1.1.1.1 of R1 is in rip area
5.5.5.5.5 of R5 is in area 4. R3 and R4 are point-to-point connections,

Type of LSA:

In this experiment, we only analyze the first 1-5 categories

The first type:
First, check whether the ospf link state database is complete on R1, and all links have been completed,

Type 1.

1. LSA like view method:

[R1]display ospf lsdb router 

First of all, this is in Area 1

	 OSPF Process 1 with Router ID 1.1.1.1
		         Area: 0.0.0.1    //region1 within
		 Link State Database 


  Type      : Router
  Ls id     : 2.2.2.2      //Destination address, this is to send the address to the local
  Adv rtr   : 2.2.2.2     //ADV RTR Is Tonggao address
  Ls age    : 669 
  Len       : 36 
  Options   :  ABR  E  
  seq#      : 80000004 
  chksum    : 0x53cd
  Link count: 1
   * Link ID: 11.1.1.2     
     Data   : 11.1.1.2     
     Link Type: TransNet     
     Metric : 1

Of course, it will also tell its own Router ID

  Type      : Router
  Ls id     : 1.1.1.1
  Adv rtr   : 1.1.1.1  
  Ls age    : 57 
  Len       : 36 
  Options   :  E  
  seq#      : 8000000a 
  chksum    : 0x82a2
  Link count: 1
   * Link ID: 11.1.1.2     
     Data   : 11.1.1.1     
     Link Type: TransNet     
     Metric : 1

Conclusion:

Characteristics: spread within the region, not across the region (within the region)
Announcement content: all links or interfaces of router, outbound cost along each link direction, and its neighbors.

Of course, it will also be found that R2 is in zone 1 and zone 0. How does it work

Of course, both areas are notified,

What's the matter?
First feature: spread within the region, not across the region (within the region)
Area1 Area0 in this area belongs to R2 in this area

Type 2.

To observe, you first need to know how to observe:
<R1>display ospf lsdb network 

	 OSPF Process 1 with Router ID 1.1.1.1
		         Area: 0.0.0.1      //region1
		 Link State Database 


  Type      : Network
  Ls id     : 11.1.1.2			//DR address
  Adv rtr   : 2.2.2.2  			//Announcement address
  Ls age    : 924 
  Len       : 32 
  Options   :  E  
  seq#      : 80000002 
  chksum    : 0xfe37
  Net mask  : 255.255.255.0
  Priority  : Low
     Attached Router    2.2.2.2
     Attached Router    1.1.1.1

Feature: DR address in this area
Announcement content: multiple access network and all routers connected to it (including subnet mask)
Note: point to point is that there is no DR,BDR election, so there is no contract

R3 view, point-to-point area 2 has no information

[R3]display ospf lsdb network 

	 OSPF Process 1 with Router ID 3.3.3.3
		         Area: 0.0.0.0
		 Link State Database 


  Type      : Network
  Ls id     : 12.1.1.2
  Adv rtr   : 3.3.3.3  
  Ls age    : 1485 
  Len       : 32 
  Options   :  E  
  seq#      : 80000002 
  chksum    : 0x2801
  Net mask  : 255.255.255.0
  Priority  : Low
     Attached Router    3.3.3.3
     Attached Router    2.2.2.2
		         Area: 0.0.0.2     // Empty information
		 Link State Database 

		         Area: 0.0.0.3
		 Link State Database 


  Type      : Network
  Ls id     : 14.1.1.2
  Adv rtr   : 5.5.5.5  
  Ls age    : 1481 
  Len       : 32 
  Options   :  E  
  seq#      : 80000003 
  chksum    : 0x46cb
  Net mask  : 255.255.255.0
  Priority  : Low
     Attached Router    5.5.5.5
     Attached Router    3.3.3.3
 
[R3]   

Type 3.

[R1]display ospf lsdb summary 

	 OSPF Process 1 with Router ID 1.1.1.1
		         Area: 0.0.0.1
		 Link State Database 


  Type      : Sum-Net
  Ls id     : 12.1.1.0
  Adv rtr   : 2.2.2.2  
  Ls age    : 437 
  Len       : 28 
  Options   :  E  
  seq#      : 80000002 
  chksum    : 0x83c1
  Net mask  : 255.255.255.0
  Tos 0  metric: 1
  Priority  : Low

  Type      : Sum-Net
  Ls id     : 14.1.1.0
  Adv rtr   : 2.2.2.2  
  Ls age    : 437 
  Len       : 28 
  Options   :  E  
  seq#      : 80000002 
  chksum    : 0x73ce
  Net mask  : 255.255.255.0
  Tos 0  metric: 2
  Priority  : Low

  Type      : Sum-Net
  Ls id     : 13.1.1.0
  Adv rtr   : 2.2.2.2  
  Ls age    : 437 
  Len       : 28 
  Options   :  E  
  seq#      : 80000002 
  chksum    : 0x80c2
  Net mask  : 255.255.255.0
  Tos 0  metric: 2
  Priority  : Low



First, class 3 LSA is sent between regions, and it transfers routes between regions. It is sent by ABR, and it can penetrate regions

ABR: in multiple areas and ABR equipment in area 0

R2 R3 is located in multiple areas, which is ABR route

  The normal area can be sent and routed to the backbone area, of course, the backbone area can also be sent back.
  Communication is not allowed between ordinary areas, which should be understood.

Horizontal division between OSPF areas,
The common area is sent to the backbone area, and the backbone area cannot be sent back, but the indirect area is feasible.

For example

Two zones 0 are not allowed in the network

Type 4.

[R2]display ospf lsdb asbr


Notification: by ABR router
Announcement content: it is an ASBR router, not a network. Others are the same as network aggregation LSA.
Area: OSPF area to area transfer,
ASBR: Border Routing

Type 5.

External LSA of autonomous system

Notification: sent by ASBR router

Announcement content: LSA of external destination or external default route of OSPF autonomous system (external route, not belonging to a specific region)
This type of LSA packet lists the external routing network segment, mask, Metric value, route tag, and publish type (E2/E1) link ID as the target network segment, and Adv Router as the ASBR router ID

Scope: this type of LSA is propagated in the whole OSPF routing domain

The analysis may not be very detailed, and it will be improved slowly.

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Tags: network Database

Posted on Wed, 04 Mar 2020 01:05:11 -0800 by ragear