You are designing a WAN network solution with EIGRP based on VPLS. The interface speed is 10Mb/s, but the access rate of the WAN connection is 256 Kb/s. What should you include in the network…

Question

Options

• ALimit EIGRP traffic to the access rate with a policer.
• BTag outbound EIGRP traffic and have the WAN provider add it to the priority queue.
• CLimit traffic to the access rate with interface traffic shaping.
• DSet the interface bandwidth to match the access rate.

• A
  16% (9)
• B
  4% (2)
• C
  9% (5)
• D
  72% (41)

Explanation

Setting the interface bandwidth to match the actual WAN access rate (256 Kb/s) is correct because EIGRP uses the interface bandwidth value for two critical purposes: calculating routing metrics and self-throttling its own control traffic (defaulting to 50% of interface bandwidth). With the interface reporting 10 Mb/s, EIGRP believes it has far more capacity than actually exists - leading to inflated link costs in metric calculations and potentially flooding the 256 Kb/s pipe with routing updates.

Why the distractors fail:

• A (Policer): Policing drops or re-marks exceeding traffic; applying it to EIGRP packets would cause them to be dropped, destabilizing neighbor adjacencies - it does nothing to fix metric calculations.
• B (Priority queuing via WAN provider): Prioritizing EIGRP traffic helps it survive congestion but doesn't correct the bandwidth mismatch; EIGRP still computes wrong metrics and still doesn't know to self-limit.
• C (Traffic shaping): Shaping buffers all outbound traffic to a rate, but again doesn't inform EIGRP of the true link capacity - metrics remain incorrect and EIGRP's self-throttle still references 10 Mb/s.

Memory tip: Think of the bandwidth command as "telling EIGRP the truth." EIGRP only knows what the interface tells it - if the interface lies (10 Mb/s), EIGRP lies too (wrong metrics, too much traffic). Match the bandwidth to reality, and EIGRP fixes itself automatically.

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