Which two statements describe the usage of the IS-IS overload bit technique? (Choose two)

Question

Options

• Alf overload-bit is set on a Level 2 intermediate system, the other Level 2 intermediate systems in
• BIt can be set in intermediate systems (IS-IS routers) to prioritize control plane CSNP packets.
• CIt can be used to automatically synchronize the link-state database between Level 1 intermediate
• DIt can be set in intermediate systems (IS-IS routers) to avoid traffic black holes until routing
• EIt can be set in intermediate systems (IS-IS routers) to attract transit traffic from other

• A
  4% (2)
• B
  9% (4)
• C
  2% (1)
• D
  85% (39)

Explanation

The IS-IS overload bit, when set on an IS-IS router, signals to all other routers in the domain that this router should not be used as a transit node for paths (other routers will still route TO it, but not THROUGH it). Choice D is correct because the primary use case is to set the overload bit during router startup or after a reload - before the routing table is fully populated - so that traffic is not black-holed by being forwarded to a router that doesn't yet have complete routing information. This is commonly paired with BGP convergence timers (e.g., 'set-overload-bit on-startup wait-for-bgp'). Choice E is correct because the overload bit can also be deliberately and permanently set for traffic engineering purposes - to prevent a specific router from attracting transit flows from the rest of the network (effectively taking it out of the transit path without tearing down adjacencies). Choice B is incorrect: the overload bit has nothing to do with CSNP packet prioritization. Choice C is incorrect: it is not a database synchronization mechanism. Choice A describes a true IS-IS behavior (Level 2 overload bit behavior) but is not among the two best descriptions of the technique's usage.

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