Redistribute IS-IS Level-1 into Level-2

In IS-IS, all areas are stub areas, which means that no routing information is leaked from the backbone (Level 2) into areas (Level 1). Level 1-only routers use default routing to the closest Level 1-Level 2 router in their area. This command enables you to redistribute Level 2 IP routes into Level 1 areas. This redistribution enables Level 1-only routers to pick the best path for an IP prefix to get out of the area. This is an IP-only feature, CLNS routing is still stub routing.

For more control and scalability, a distribute list or a route map can control which Level 2 IP routes can be redistributed into Level 1. This command allows large IS-IS-IP networks to use areas for better scalability.
Examples

In the following example, access list 100 controls the redistribution of IS-IS from Level 1 into Level 2:

router isis
net 49.0000.0000.0001.00
metric-style wide
redistribute isis ip level-1 into level-2 distribute-list 100
!
access-list 100 permit ip 10.10.10.0 0.0.0.255 any


In the following example, the route map named "match-tag" controls the redistribution of IS-IS from Level 1 into Level 2 so that only routes tagged with 110 are redistributed:

router isis
net 49.0000.0000.0001.00
metric-style wide
redistribute isis ip level-1 into level-2 route-map match-tag
!
route-map match-tag permit 10
match tag 110
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