network-interface-health
Diagnose interface errors, drops, CRCs, duplex mismatches, flapping, speed negotiation issues, and counter trends on routers, switches, and Linux hosts. Use when an interface shows errors, drops, CRCs, flapping, or a duplex or speed mismatch.
- Kind
- Skill
- Works with
- Claude Code, Codex
- Source
- affaan-m/ECC @ d3b8a3e90890
- Path
- skills/network-interface-health/SKILL.md
- License
- MIT
- Jobs
- Debugging
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# Network Interface Health Use this skill when a network symptom might be caused by a physical link, switch port, cable, transceiver, duplex setting, or congested interface. ## When to Use - A host or VLAN has packet loss, latency spikes, or intermittent reachability. - A switch or router interface shows CRCs, runts, giants, drops, resets, or flaps. - You need to compare both ends of a link before replacing hardware. - A change window needs before/after interface counter evidence. - Monitoring reports rising `ifInErrors`, `ifOutErrors`, or `ifOutDiscards`. ## How It Works Interface counters are evidence, but the trend matters more than the absolute number. Capture a baseline, wait a measurement interval, capture again, then compare increments. ```text show interfaces <interface> show interfaces <interface> status show logging | include <interface>|changed state|line protocol ``` On Linux hosts: ```text ip -s link show <interface> ethtool <interface> ethtool -S <interface> ``` ## Counter Reference | Counter | Meaning | Common cause | | --- | --- | --- | | CRC | Received frame checksum failed | Bad cable, dirty fiber, bad optic, duplex mismatch | …