Controlling Granularity of Routing Information

You can force the distribution of level 2 routing information to level 1 routers in other areas to improve the quality of the resulting routes, but at the cost of reduced scalability.

distribute-domain-wide

• Use to increase the granularity of routing information within a domain.
• Domainwide prefix distribution enables a routing domain running with both level 1 and level 2 IS-IS routers to distribute IP prefixes from level 2 to level 1 between areas.
• The major advantage for using domainwide prefix distribution is to improve the quality of the resulting routes within a domain by distributing more specific information.
• The major disadvantage of using domainwide prefix distribution is that it affects the scalability of IS-IS. When used, it increases the number of prefixes throughout the domain, causing increased memory consumption, transmission requirements, and computation requirements throughout the domain.
• A trade-off decision must be made between scalability and optimality.
• Issue this command from within the IS-IS IPv6 address family to increase the granularity of IPv6 routing information within a domain.
• Example

  host1(config-router)#distribute-domain-wide

• Use the no version to halt the distribution of routes from level 2 to level 1.
• See distribute-domain-wide

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