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Network+ Exam

interface statistice

October 29, 2025

  • #network+

interface statistice

link state- communicates weather an interface is up or down.

reliability

txload

rxload

drop - number that have been dropped

flush - sounts selective pact discards

spd - DISCARDS lower priority packets.

throttle - interface fails to buffer current flow

CRC - number of packets that recived but do not match the checksum

frame - number of packets where a crc non over ru

Igored

📡 Interface & Link-State Monitoring

Purpose:

Track the health and performance of network interfaces (router, switch ports). Helps with troubleshooting and capacity planning.

🔑 Key Metrics

  • Link State
    • Shows if an interface is up or down.
    • If down → cable, port, or hardware failure.
  • Reliability
    • Measure of interface stability.
    • Expressed as a value (higher = more reliable).
  • Txload (Transmit Load)
    • Load on the outbound (sending) traffic.
    • Indicates how much of the available bandwidth is being used.
  • Rxload (Receive Load)
    • Load on the inbound (receiving) traffic.
    • Shows if the interface is saturated with incoming data.

📉 Error & Drop Counters

  • Drop
    • Packets dropped due to congestion or buffer overflow.
  • Flush
    • Selective packet discards (often due to QoS policy).
  • SPD (Selective Packet Discard)
    • Router/switch discards lower-priority packets first when congested.
  • Throttle
    • Indicates the interface is unable to buffer/handle current traffic load.
  • CRC Errors (Cyclic Redundancy Check)
    • Packets received but checksum doesn’t match.
    • Often due to cabling issues, interference, or duplex mismatch.
  • Frame Errors
    • Corrupted frames that fail checks beyond CRC.
    • Could indicate alignment or physical layer problems.
  • Ignored
    • Packets dropped because the interface input queue was full.
    • Indicates buffer/queue overflow.

✅ Exam Tips

  • Link-state up/down = physical or Layer 1 status.
  • Txload/Rxload = utilization (capacity vs actual load).
  • CRC/frame errors = Layer 1 issues (bad cables, interference).
  • Ignored/Drop/Throttle = congestion or buffer problems.
  • SPD/Flush = QoS-related selective discards.

⚡ Sample Question:

“An interface shows increasing CRC errors. What is the most likely cause?”

→ Faulty cabling or physical interference.

🛠️ Interface/Link-State Troubleshooting Cheat Sheet

| Metric / Symptom | Likely Cause | | --- | --- | | Link state down | Cable unplugged, bad port, power failure, or hardware fault. | | High Txload / Rxload | Interface congestion, bandwidth saturation, too much traffic. | | Drops increasing | Queue/buffer overflow due to congestion. | | Flush (selective discards) | QoS policy dropping packets selectively. | | SPD (Selective Packet Discard) | Router/switch dropping low-priority packets under congestion. | | Throttle events | Interface unable to buffer → too much traffic for current speed/CPU. | | CRC errors | Faulty cabling, bad connectors, interference, duplex mismatch, or damaged NIC. | | Frame errors | Alignment errors, collisions, physical layer faults, or bad transceivers. | | Ignored packets | Input queue full (buffer overflow), device overwhelmed. | | High error rate overall | Misconfigured speed/duplex, bad cabling, failing hardware, EMI/RFI interference. |

✅ Exam Tips

  • CRC = bad cables / interference.
  • Drops/Ignored = congestion/buffers full.
  • SPD/Flush = QoS discarding lower-priority packets.
  • Link state = Layer 1 issue (cable/port).
  • Txload/Rxload = traffic utilization.

⚡ Sample Question:

A switch port shows rising CRC errors but low utilization. What’s the most likely issue?

→ Bad cable or interference (physical layer problem).