Configure IS-IS DIS Node Selection

Network Requirements

• Specify the device as the DIS node by changing the priority.
• Device1 and Device2 are the Level-1-2 devices, Device3 is the Level-1 device, and Device4 is the Level-2 device. Device1, Device2, Device3, and Device4 are in the same broadcast network and in the same area, Area 10.

Network Topology

Figure 9–2 Networking of configuring the IS-IS DIS selection

Configuration Steps

Step 1: Configure the IP address of the interfaces. (Omitted)

Step 2: Configure the IS-IS and enable the process on the interface.

#Configure the IS-IS process as 100, area number as 10, and type as Level-1-2 and enable the process on the interface on Device1.

#Configure the IS-IS process as 100, area number as 10, and type as Level-1-2 and enable the process on the interface on Device2.

#Configure the IS-IS process as 100, area number as 10, and type as Level-1 and enable the process on the interface on Device3.

#Configure the IS-IS process as 100, area number as 20, and type as Level-2 and enable the process on the interface on Device4.

Device4#configure terminal
Device4(config)#router isis 100
Device4(config-isis)#net 20.0000.0000.0004.00
Device4(config-isis)#is-type level-2
Device4(config-isis)#metric-style wide
Device4(config-isis)#exit
Device4(config)#interface vlan2
Device4(config-if-vlan2)#ip router isis 100 
Device4(config-if-vlan2)#exit

Device1#show isis neighbors  
IS-IS Instance 100 Neighbors (Counter 4): 
Type   System ID      Interface  State Holdtime Level IETF-NSF Priority Circuit ID 
L1-LAN 0000.0000.0002 vlan2      Up    23 sec   L1    capable  64       0000.0000.0003.01 
L2-LAN 0000.0000.0002 vlan2      Up    23 sec   L2    capable  64       0000.0000.0004.01 
L1-LAN 0000.0000.0003 vlan2      Up    8 sec    L1    capable  64       0000.0000.0003.01 
L2-LAN 0000.0000.0004 vlan2      Up    8 sec    L2    capable  64       0000.0000.0004.01 

The pseudo node of Level-1 is 0000.0000.0003.01 and Device3 is the DIS node of Level-1. The pseudo node of Level-2 is 0000.0000.0004.01 and Device1 is the DIS node of Level-2.

#Run the show isis interface command to view the MAC address of the interface. In the default priority, the DIS node is selected based on the principle that a larger MAC address of the physical interface has a higher priority.

Step 3: Modify the interface priority.

#Modify the interface priority of Device1.

Step 4: Check the result.

#View the IS-IS neighboring information of Device1.

Device1#show isis neighbors  
IS-IS Instance 100 Neighbors (Counter 4): 
Type    System ID      Interface  State Holdtime  Level IETF-NSF Priority Circuit ID 
L1-LAN  0000.0000.0002 vlan2      Up    24 sec    L1    capable  64       0000.0000.0001.01 
L2-LAN  0000.0000.0002 vlan2      Up    23 sec    L2    capable  64       0000.0000.0001.01 
L1-LAN  0000.0000.0003 vlan2      Up    20 sec    L1    capable  64       0000.0000.0001.01 
L2-LAN  0000.0000.0004 vlan2      Up    24 sec    L2    capable  64       0000.0000.0001.01 

The pseudo node of Level-1-2 is 0000.0000.0001.01 and Device1 is the DIS node of Levev-1-2.

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  The IS-IS interface priority is 64 by default.

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