When you have a strange network problem on a fiber uplink you may experience this output in display interface command:
<CAMPUS-glitchlist_lab>dis int gi0/0/12 GigabitEthernet0/0/12 current state : UP Line protocol current state : UP Description:to SPINE1 Switch Port, Link-type : trunk(configured), PVID : 1, TPID : 8100(Hex), The Maximum Frame Length is 9216 IP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is 7cc3-8560-2e22 Last physical up time : 2019-03-24 21:34:42 Last physical down time : 2019-03-24 21:34:13 Current system time: 2019-03-27 23:05:07 Port Mode: COMMON FIBER, Transceiver: 1000_BASE_SX_SFP Speed : 1000, Loopback: NONE Duplex: FULL, Negotiation: DISABLE Mdi : -, Flow-control: DISABLE Last 300 seconds input rate 358736 bits/sec, 313 packets/sec Last 300 seconds output rate 6193032 bits/sec, 616 packets/sec Input peak rate 36127856 bits/sec, Record time: 2019-03-17 01:01:27 Output peak rate 73339616 bits/sec, Record time: 2019-03-27 14:47:37 Input: 124841580 packets, 40279782184 bytes Unicast: 124051275, Multicast: 121188 Broadcast: 139931, Jumbo: 0 Discard: 0, Pause: 0 Frames: 0 Total Error: 529186 CRC: 0, Giants: 0 Runts: 0, DropEvents: 0 Alignments: 0, Symbols: 529186 Ignoreds: 0 Output: 173537172 packets, 195364958288 bytes Unicast: 172372334, Multicast: 871683 Broadcast: 293155, Jumbo: 0 Discard: 0, Pause: 0 Total Error: 0 Collisions: 0, Late Collisions: 0 Deferreds: 0 Input bandwidth utilization threshold : 80.00% Output bandwidth utilization threshold: 80.00% Input bandwidth utilization : 0.04% Output bandwidth utilization : 0.62%
The error Symbols: 529186 generate link flappings many times a day.
Ethernet RFCs describe how to place an L2 frame in the physical layer (L1), 8B/10B encoding process takes 8bit of Media Access Control Layer and converts it in a 10bit symbol to encapsulate it on the physical media.
When this error happens It means:
- You have CRC on fiber/copper cable because of a physical problem.
- The encoding process is not the same at both ends of the link.
If your link is good, something happened on the link. Almost surely a Media Converter has been added or removed. this action caused an anomaly in the transmission of symbols on a physical level.
To solve the problem it is necessary to renegotiate the ports of the link by setting them at a fixed speed, then shut and no shut will solve the problem forever.