A network engineer is troubleshooting performance issues across several switch interfaces using Cisco IOS CLI outputs. Match each interface status or error counter symptom on the left to its corresponding Layer 1 or Layer 2 root cause on the right.
- Interface shows incrementing 'late collisions' and FCS errors on a local interface set to half-duplex while experiencing poor throughput.Duplex mismatch resulting from the remote device operating in full-duplex mode while the local port operates in half-duplex mode.
- Interface shows status 'GigabitEthernet0/1 is down, line protocol is down' when connecting two switch interfaces with Auto-MDIX disabled using a straight-through cable.Pinout misconfiguration between identical MDI-X interfaces requiring a crossover cable when auto-negotiation features are inactive.
- Interface shows status 'GigabitEthernet0/2 is up, line protocol is down (disabled)' accompanied by encapsulation error messages.Layer 2 framing or keepalive mismatch between connected endpoints causing data-link failure while physical signaling remains active.
- Interface shows incrementing 'giants' and CRC errors on an Ethernet port receiving traffic from a server.End-host network interface card (NIC) transmitting babbling/oversized frames exceeding the standard Maximum Transmission Unit (MTU).
Cevap
Each interface symptom matches its specific root cause based on Cisco IOS interface operation: Late collisions match a duplex mismatch; physical down/down with straight-through and disabled Auto-MDIX matches pinout misconfiguration requiring a crossover cable; up/down (disabled) matches Layer 2 framing or keepalive failure; incrementing giants with CRC errors matches oversized frame transmission exceeding MTU.
Each symptom accurately maps to its fundamental physical or data-link root cause: late collisions indicate duplex mismatch; down/down with straight-through cabling on switch-to-switch links without Auto-MDIX indicates incorrect pinout; up/down indicates Layer 2 framing/keepalive failure; and giants indicate frames received that exceed the allowable maximum frame size.
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Anahtar Kavram
Cisco IOS Interface Counter Analysis and Physical/Data-Link Troubleshooting