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Principle and configuration of IS-IS

2022-05-15 07:26:18zljszn

One 、IS-IS Basic concepts of

NSAP Similar to our TCP/IP Layer IP Address , It's also used to identify ,IDI Used to represent a geographical area ,High Order DSP What we often see is 49 position , hinder 0001 It means area , It usually means private network address ,System ID Is similar to the router id, It can't be overlapped ,SEL If 0 It means working in ip In the environment of network layer , In daily configuration, we don't need to configure NSAP But it needs to be configured NET

Router classification :

level-1: Level 1 , Maintenance only L1 The neighbor relationship of the router is similar to L1 Level link state information LSDB, If a level in an area is 1 Another level is 2 You can't build a neighborhood

When the grades are the same :

When the grades are inconsistent :

 

It can be in the same area or in different areas L2 Router .L1/L2 The router establishes a neighbor relationship , Maintainer L2 Of LSDB, Including the whole IS All routing information of the domain  

 

Only in L2 Router under level , Then we can establish neighborhood relations in different areas , All continuous L2 The collection of routers is called backbone area  

  You can talk to L1 The hierarchical router establishes the adjacency relationship of the same area , and L2 Establish adjacency between the same or different regions ,

Maintain this L1 and L2 Of LSDB, Be similar to ospf Medium ABR, Can establish adjacency relationship with all routers

  As shown in the verification diagram above ,g0/0/0 The interface is connected to the left L1 Level router , that g0/0/1 Connected to the right L2 Level router , The rendering is a L1-2 Level router , indicate L1-2 You can talk to L1 and L2 Level routers establish neighbor relationships

that isis There are only two types of networks , One is broadcasting , The other is point-to-point  

1、 Interface overhead : That is, set the cost for a single interface :[Huawei-GigabitEthernet0/0/0]isis cost

2、 Global overhead : Set the overhead for all interfaces :[Huawei-isis-1]circuit-cost

3、 Automatically calculate overhead : That is, automatically calculate his bandwidth according to the bandwidth :[Huawei-isis-1]auto-cost enable 

Message type :

IIH(IS-IS Hello) : It is divided into L1 hello、L2 hello、P2P hello message ,L1 hello、L2 hello Applicable to broadcast message ,P2P hello The message is applicable to point-to-point network

LSP(Link State PDU): It is divided into L1 LSP、L2 LSP

CSNP( Full serial number message ): Used to synchronize LSP, Be similar to ospf Of DD message

PSNP( Part of the serial number message ): Be similar to ospf Of LSR、LSACK message

isis The principle of establishing adjacency relationship :

Only adjacent routers at the same level can become adjacent

about Level-1 For routers ,Area ID It has to be consistent

Both ends of the link IS-IS The network type of the interface must be consistent

Both ends of the link IS-IS The address of the interface must be in the same network segment ( By default )

The establishment process of adjacency relationship in broadcast network

1、 stay Down State, ,R1 Multicast send Level-1 LAN IIH, The adjacency list in this message is empty .

2、R2 After receiving this article , Identify the adjacency status as Initial. then ,R2 Again to R1 reply Level-1 LAN IIH , This message identifies R1 by R2 Adjacency of

3、R2 After receiving this article , Identify the adjacency status as Initial. then ,R2 Again to R1 reply Level-1 LAN IIH , This message identifies R1 by R2 Adjacency of

4、R2 After receiving this article , Identify the adjacency status as Initial. then ,R2 Again to R1 reply Level-1 LAN IIH , This message identifies R1 by R2 Adjacency of

5、 Elections are needed in broadcast networks DIS, After the adjacency relationship is established , The router will wait for two Hello Message interval , Proceed again DIS The election of .

DIS( Specify the intermediate system )

1、 stay IS-IS In the broadcast network , The priority for 0 Your router is also involved DIS The election of , And in the OSPF Medium priority is 0 Your router is not involved DR The election of

2、 stay IS-IS In the broadcast network , When a new router joins , And conform to become DIS The condition of , This router will be selected as the new DIS, The original pseudo node is deleted . This change will cause a new set of LSP flooding . And in the OSPF in , When a new router joins , Even if it's DR The priority value is the maximum , It will not immediately become the DR 

3、 stay IS-IS In the broadcast network , Adjacent relationships will be formed between routers at the same level on the same network segment , Including all non DIS There will also be adjacency between routers . And in the OSPF in , The router only works with DR and BDR Establish adjacency

DIS Election rules :

1、 Compare the priority value of the interface , Those with large values will be selected as DIS

2、 Compare MAC Address ,MAC Those with large addresses will be directly selected as DIS

Establishment of adjacency relationship in point-to-point network :

 P2P In the network, two handshakes and three handshakes are used to establish adjacency relationship , Huawei uses three handshakes to establish adjacency by default

IS-IS Of LSDB

The red box in front is not 0 Said is DIS( Generated by pseudo nodes ), The red box in the back is not 0 Then it means fragment ,isis Of LSP It supports slicing ,* It means that it is produced by itself LSP

View the of non pseudo nodes LSP:

SOURCE       0000.0000.0001.00          //system id

NLPID          IPV4                                   //IPV4 edition

AREA ADDR    49.0000                          // Area number

INTF ADDR    1.1.1.1                              // Address of the interface , There are several IP There are just a few addresses, this

NBR  ID      0000.0000.0001.01              // Connected neighbors system id, Back non 0 said DIS

IP-Internal  1.1.1.1         255.255.255.255  COST: 0     // This is ip Routing information

View the of pseudo nodes LSP:

Pseudo node LSP It's simpler , Just check which neighbors are connected  , There is no route

CSNP:

isis It's through CSNP Synchronization LSDB, Be similar to ospf Medium DD message , On the broadcast network :isis There will be no route immediately after establishing a neighbor , But after a while , because CSNP Every time 10 Seconds to send , Therefore, after establishing a good neighbor relationship, you need to wait for a period of time before you have routing information . So in a point-to-point network : Will send... The first time an adjacency relationship is established

PSNP

PSNP: Is used to request LSP Message and confirmation LSP message , Is similar to the ospf Medium LSR Follow LSACK message  

In the broadcast network LSP The synchronization process of :

 1、 New router R3 First send IIH message , Establish an adjacency relationship with the router in the broadcast domain . After establishing adjacency ,R3 wait for LSP Refresh timer timeout , Then put your own LSP Send to multicast address (Level-1:01-80-C2-00-00-14;Level-2:01-80-C2-00-00-15). In this way, all neighbors on the network will receive the LSP

2、 In this segment DIS I'll send you R3 Of LSP Add to LSDB in , And wait for CSNP The message timer timed out and sent CSNP message

3、R3 received DIS It's from CSNP message , Compare your own LSDB database , And then to DIS send out PSNP The message requests what it doesn't have LSP

4、DIS Received this PSNP Message request backward R3 Send the corresponding LSP Conduct LSDB Synchronization of      

In Peer-to-Peer Networks LSP The synchronization process of :

1、R1 With the first R2 Establish adjacency

2、 After establishing adjacency ,R1 And R2 Will send CSNP To the opposite device . If the end to end LSDB And CSNP There is no synchronization , Then send PSNP Ask for the corresponding LSP 

Routing calculation :

L1 Of the area in which it is located L1/L2 The router will send a message containing ATT Set up LSP,L1 When the router receives it , Calculate a default route , The next jump is L1/L2 Router

What is? ATT Set up :

ATT The setting contains routing information  

The problem of router suboptimal path :

  because R1 stay L1 Inside the area , So he doesn't know how to get the external route , So go to R2 Follow R3 It's all the same path , So there will be a suboptimal path

terms of settlement :

stay L1/L2 Route penetration on the router L2 Routing information of the introduced area L1 In the area , here L1 The router knows L2 Routing information of the area , In this way, the best route can be calculated

Experimental chart :

Configuration code : stay L1/L2 Level router R2 Do routing penetration on , Generally at the end of the optimal path L1/L2 Do... On the router

isis 1

import-route isis level-2 into level-1

Let's check the routing table to arrive at R3 Return loop of 3.3.3.3 There is only one detailed route , The problem of suboptimal path will not appear

L1/L2 Routing calculation of router :

Will also maintain L1/L2 Of LSDB, hold L1 Of LSP With L2 Of LSP Send to the backbone area in the form of , So the backbone router can learn the routes of all non backbone routers

L2 Routing calculation of router :

maintain L2 Level router LSDB, They can according to the LSDB Calculate the route to each network segment of the whole network .

isis Certification of :

1、 Interface authentication : Configure... In the interface view , Yes Level-1 and Level-2 Of Hello Message authentication  

2、 Regional certification : stay IS-IS Configure in the process view , Yes Level-1 Of CSNP、PSNP and LSP Message authentication

3、 Routing domain authentication : stay IS-IS Configure in the process view , Yes Level-2 Of CSNP、PSNP and LSP Message authentication

1、 Detailed explanation of interface authentication :Hello The authentication password used in the message is saved under the interface , Send with authentication TLV Authentication message of , The router interfaces connected to each other must be configured with the same password

2、 Regional certification : Every machine in the area L1 All routers must use the same authentication mode and have a common key chain

3、 Road area certification :IS-IS Every machine in the domain L2 and L1/L2 All types of routers must use the same authentication mode , And use a common key chain

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