Administrator Guide

In IS-IS, neighbors form adjacencies only when they are same IS type. For example, a Level 1 router never forms an adjacency
with a Level 2 router. A Level 1-2 router forms Level 1 adjacencies with a neighboring Level 1 router and forms Level 2
adjacencies with a neighboring Level 2 router.
NOTE: Even though you enable IS-IS globally, enable the IS-IS process on an interface for the IS-IS process to exchange
protocol information and form adjacencies.
To configure IS-IS globally, use the following commands.
1. Create an IS-IS routing process.
CONFIGURATION mode
router isis [tag]
tag: (optional) identifies the name of the IS-IS process.
2. Configure an IS-IS network entity title (NET) for a routing process.
ROUTER ISIS mode
net network-entity-title
Specify the area address and system ID for an IS-IS routing process. The last byte must be 00.
For more information about configuring a NET, refer to IS-IS Addressing.
3. Enter the interface configuration mode.
CONFIGURATION mode
interface interface
Enter the keyword interface then the type of interface and slot/port information:
● For a 1-GigabitEthernet interface, enter the keyword GigabitEthernet then the slot/port information.
● For a 10-Gigabit Ethernet interface, enter the keyword TenGigabitEthernet then the slot/port information.
● For a Loopback interface, enter the keyword loopback then a number from 0 to 16383.
● For a port channel interface, enter the keywords port-channel then a number.
● For a VLAN interface, enter the keyword vlan then a number from 1 to 4094.
4. Enter an IPv4 Address.
INTERFACE mode
ip address ip-address mask
Assign an IP address and mask to the interface.
The IP address must be on the same subnet as other IS-IS neighbors, but the IP address does not need to relate to the NET
address.
5. Enter an IPv6 Address.
INTERFACE mode
ipv6 address ipv6-address mask
● ipv6 address: x:x:x:x::x
● mask: The prefix length is from 0 to 128.
The IPv6 address must be on the same subnet as other IS-IS neighbors, but the IP address does not need to relate to the
NET address.
6. Enable IS-IS on the IPv4 interface.
ROUTER ISIS mode
ip router isis [tag]
If you configure a tag variable, it must be the same as the tag variable assigned in step 1.
7. Enable IS-IS on the IPv6 interface.
ROUTER ISIS mode
ipv6 router isis [tag]
If you configure a tag variable, it must be the same as the tag variable assigned in step 1.
The default IS type is level-1-2. To change the IS type to Level 1 only or Level 2 only, use the is-type command in ROUTER
ISIS mode.
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Intermediate System to Intermediate System