Explains multi-instance IS-IS operations, including configuration approaches and restrictions encountered when implementing multiple IS-IS instances on Cisco platforms.
Multi-instance IS-IS instance is a routing protocol feature that
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allows you to configure up to 16 separate IS-IS instances on a device
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enables MPLS to operate on multiple IS-IS processes when they run on distinct sets of interfaces, and
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prevents double-booking by enforcing that each interface associates with only one IS-IS instance, generating configuration errors if violated.
Each IS-IS instance is treated equally by the Routing Information Base (RIB). When redistributing routes between instances, the RIB does not automatically prefer Level 1 over Level 2 routes. You must manually enforce route preference by setting different administrative distances for each instance type.