IS-IS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

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Mesh groups

Updated: June 9, 2026

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Describes mesh group concepts used to optimize protocol flooding and enhance scalability in complex network topologies.

A mesh group is a router interface set that

  • limits flooding by restricting Link State Packet propagation,

  • ensures network resilience by assuming dense connectivity between routers, and

  • optimizes IS-IS behavior for stable operations.

Routers reachable via mesh group interfaces are assumed to be closely interconnected, with at least one redundant link connecting each router to every other router. This arrangement allows multiple links to fail without isolating any routers, maintaining network integrity.

In normal flooding, a new LSP received on an interface is flooded out all other interfaces. With mesh groups, when a new LSP is received over a mesh group interface, it is not flooded over other mesh group interfaces, reducing unnecessary traffic.