If an IS-IS device needs to be temporarily isolated, configure the IS-IS device to enter the overload state to prevent other devices from forwarding traffic to this IS-IS device and prevent blackhole routes.
If an IS (for example, an IS to be upgraded or maintained) needs to be temporarily isolated, configure the IS to enter the overload state so that no device will forward traffic to this IS.
IS-IS routes converge more quickly than BGP4+ routes. To prevent blackhole routes on a network where both IS-IS and BGP4+ are configured, set an overload bit to instruct an IS to enter the overload state during its start or restart. After BGP convergence is complete, cancel the overload bit.
isis [ process-id ]
set-overload [ on-startup [ timeout1 | start-from-nbr system-id [ timeout1 [ timeout2 ] ] | wait-for-bgp [ timeout3 ] ] [ send-sa-bit [ timeout3 ] ] ] [ allow { interlevel | external } * ]