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
![Networking of configuring the IS-IS DIS selection](/storage/images/Document/Maipu/unicast-routing/config-is-is-selection.jpg)
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.
Device1#configure terminal
Device1(config)#router isis 100
Device1(config-isis)#net 10.0000.0000.0001.00
Device1(config-isis)#metric-style wide
Device1(config-isis)#exit
Device1(config)#interface vlan2
Device1(config-if-vlan2)#ip router isis 100
Device1(config-if-vlan2)#exit
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#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.
Device2#configure terminal
Device2(config)#router isis 100
Device2(config-isis)#net 10.0000.0000.0002.00
Device2(config-isis)#metric-style wide
Device2(config-isis)#exit
Device2(config)#interface vlan2
Device2(config-if-vlan2)#ip router isis 100
Device2(config-if-vlan2)#exit
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#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.
Device3#configure terminal
Device3(config)#router isis 100
Device3(config-isis)#net 10.0000.0000.0003.00
Device3(config-isis)#is-type level-1
Device3(config-isis)#metric-style wide
Device3(config-isis)#exit
Device3(config)#interface vlan2
Device3(config-if-vlan2)#ip router isis 100
Device3(config-if-vlan2)#exit
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#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.
Device1(config)#interface vlan2
Device1(config-if-vlan2)#isis priority 100
Device1(config-if-vlan2)#exit
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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.
![note](/storage/images/Document/Maipu/note-icon.jpg)
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The IS-IS interface priority is 64 by default.