A network administrator is diagnosing physical layer and data link layer interface issues on Cisco Catalyst switches. Match each Cisco IOS interface state and CLI error counter signature on the left to its primary physical or configuration root cause on the right.
- Interface is up, line protocol is down, accompanied by rapidly incrementing runts, giants, and frame alignment errors on a copper Ethernet link.Physical cable damage, excessive copper cable length, or severe Near-End Crosstalk (NEXT).
- Interface is up, line protocol is up, accumulating a high number of late collisions and FCS errors during high-volume data transmission.Duplex mismatch where the local switch interface is set to half-duplex and the connected peer operates in full-duplex.
- Interface is down, line protocol is down (notconnect) on a 1000BASE-SX fiber link where transmit lasers are confirmed active at both ends.Fiber strand polarity reversal (Tx and Rx optical patch strands swapped at one connector).
- Interface is up, line protocol is up, showing continuously incrementing deferred frame counters and normal collisions, with zero late collisions or FCS errors.Standard CSMA/CD backoff behavior on a heavily utilized half-duplex Ethernet segment.
Cevap
The correct matches pair: (1) Runts, giants, and alignment errors with physical cable corruption or NEXT; (2) Late collisions and FCS errors with a local half-duplex mismatch; (3) Fiber link down despite active lasers with Tx/Rx polarity reversal; (4) Deferred frames without late collisions or FCS errors with standard half-duplex CSMA/CD backoff.
Each physical symptom maps to its exact root cause: distorted frame dimensions (runts/giants) result from signal corruption or bad cabling; late collisions stem from full/half duplex mismatch timing conflicts; down fiber links with active lasers indicate swapped Tx/Rx strands; and deferred frames without errors represent normal half-duplex CSMA/CD deferral behavior.
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Anahtar Kavram
Cisco IOS Interface Counters and Physical Layer Diagnostics