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Routing & Switching · Advanced

Overload Bit

An IS-IS LSP flag telling other routers not to use this router for transit traffic.

Definition

When the overload (OL) bit is set, other routers compute paths that avoid transiting the router, but its directly connected prefixes remain reachable. It is set at boot until BGP converges or during maintenance. OSPF's equivalent is max-metric router-lsa.

Example

set-overload-bit on-startup wait-for-bgp

Exam tip

Setting the overload bit is the IS-IS answer for graceful traffic draining before maintenance.

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