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Establishment of IS-IS neighbor relationships-broadcast link

Latest reply: Dec 27, 2018 08:23:58 1138 8 10 0 0

Establishment of IS-IS neighbor relationships.

Two routers running IS-IS must first establish a neighbor relationship before implementing the routing function of the protocol packets.

IS-IS neighbors are established differently on different types of networks.

Establishment of broadcast link neighbor relationships.


Figure 1 shows the process of establishing a neighbor relationship in a broadcast link by taking a Level-2 router as an example. 

The neighbors are established between Level-1 routers.


Figure 1 Broadcast link neighbor relationship establishment process.


140424j11fn6zmlcnzxn21.png


1. Router A broadcasts Level-2 LAN IIH. There is no neighbor identifier in this packet.


2. After receiving the packet, Router B identifies the neighbor status of Router A and Router A as Initial. 

Router B then replies to Level 2 LAN IIH to Router A. This packet identifies Router A as the neighbor of Router B.


3. After receiving the packet, Router A identifies the neighbor status of Router B as Up.

 RouterA then sends a Level-2 LAN IIH to RouterB that identifies RouterB as the neighbor of RouterA.


4. After receiving the packet, Router B identifies the neighbor status of Router A and Router A as Up. 

In this way, the two routers successfully establish a neighbor relationship.


Because it is a broadcast network, you need to elect a DIS. Therefore, after the neighbor relationship is established, 

the router waits for the interval between two Hello packets and then performs the election of the DIS. 

The Hello message contains the Priority field. The one with the highest priority value will be elected as the DIS of the broadcast network. 

If the priorities are the same, the interface with the larger MAC address is elected as the DIS.

This is what I want to talk about/share with you today, thank you!

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dagui
Created Dec 25, 2018 06:26:00

After receiving the packet, Router A identifies the neighbor status of Router B as Up.Can you provide a more detailed explanation?
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yiyi0519
Created Dec 25, 2018 06:54:42

In large metropolitan area networks, we generally use ISIS as the IGP protocol, and the port is configured as P2P, Broadcast type networks need to choose DIS, now less applied
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xiaomumu
Created Dec 25, 2018 08:03:42

We know the basic principles of these two kinds of neighborhood relations
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YOO
Created Dec 25, 2018 08:31:20

The Hello message contains the Priority field. The one with the highest Priority value will be elected as the DIS of the broadcast network.can you share more knowlege on this topic?
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user_2915719
Created Dec 25, 2018 09:16:27

This tutorial is good for reference. What if the communication was broken while building a neighborhood relationship, will it start it over from the beginning?
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Mysterious.color
Created Dec 25, 2018 13:52:10

thanks for sharing and good information
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DZKM
Created Dec 27, 2018 08:22:02

routers running IS-IS must first establish a neighbor relationship before implementing the routing function of the protocol packets.

IS-IS neighbors are established differently on different types of networks.



Establishment of broadcast link neighbor relationships




Figure 1 shows the process of establishing a neighbor relationship in a broadcast link by taking a Level-2 router as an example.
!!!!!
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Hain
Created Dec 27, 2018 08:23:58

The Hello message contains the Priority field. The one with the highest Priority value will be elected as the DIS of the broadcast network.can you share more knowlege on this topic?
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  • x
  • convention:

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