Enabling Fault Finder

Enter this CLI command to enable fault detection:

Syntax: 


no fault-finder [fault][sensitivity <low|medium|high>][action <warn|warn-and-disable>]

Enables or disables Fault Finder and sets sensitivity.

When the warn-and-disable action option is configured, Fault Finder may also shut down a bad port in addition to sending an alert to the Alert Log.

Default setting: fault-finder sensitivity medium action warn

[fault]: Supported values are:

  • all: All fault types
  • bad-driver: Too many undersized/giant packets
  • bad-transceiver: Excessive jabbering
  • bad-cable: Excessive CRC/alignment errors
  • too-long-cable: Excessive late collisions
  • over-bandwidth: High collision or drop rate
  • broadcast-storm: Excessive broadcasts
  • duplex-mismatch-HDx: Duplex mismatch. Reconfigure to Full Duplex
  • duplex-mismatch-FDx: Duplex mismatch. Reconfigure port to Auto
  • link-flap: Rapid detection of link faults and recoveries
  • loss-of-link: Link loss detected. (Sensitivity not applicable)

Examples:

To set Fault Finder with a high sensitivity to issue a warning and then disable a port on which there is a high collision or drop rate, you could configure these options: 

switch(config)# fault-finder over-bandwidth sensitivity 
high action warn-and-disable

To set Fault Finder with a medium sensitivity to issue a warning about excessive CRC or alignment errors on a port, you could configure these options: 

switch(config)# fault-finder bad-cable sensitivity 
medium action warn

To set Fault Finder with a low sensitivity to issue a warning about rapid detection of link faults, you could configure these options: 

switch(config)# fault-finder link-flap sensitivity 
low action warn

To disable Fault Finder, enter this command: 

switch(config)# no fault-finder all
Fault finder sensitivities for supported conditions

Condition triggering fault finder

Sensitivities

Units (in packets)

Time period

Fault finder reacts:

  High Medium Low      

Bad driver — Too many under-sized packets or too many giant packets

6

21

36

1/10,000 Incoming

20 secs

If (undersized/total) >= (sensitivity/10,000)OrIf (giant/total) >= (sensitivity/ 10,000)

Bad transceiver — Excessive jabbering -Jabbers: (Jabbers are packets longer than the MTU) -Fragments: (packets shorter than they should be)

65

2110

3614

1/10,000 IncomingOne Fragments

20 secs20 secs

If (jabbers/total) >= (sensitivity/10,000)Or If fragment count in the last 20 seconds >= sensitivity

Bad cable — Excessive CRC/ alignment errors

6

21

36

1/10,000 Incoming

20 secs

If (CRC and alignment errors/ total) >= (sensitivity/10,000)

Too Long Cable — Excessive late collisions (a late collision error occurs after the first 512 bit times)

6

21

36

1/10,000 Outgoing

20 secs

If (late collisions/total) >= (sensitivity/10,000)

Over bandwidth -High collision rate -High drop rate

665

21257

36449

1/10,000 OutgoingOne Packet

5 mins5 mins

If (excessive collisions/total) >= (sensitivity/10,000)The count of dropped packets >= sensitivity during the last 5 minutes.

Broadcast storm — Excessive broadcasts

1475

5000

8525

One Broadcast Packet

1 sec

If the average per second of broadcast packets in the last 20 seconds >= sensitivity

Muticast storm — Excessive multicasts

1475

5000

8525

One Multicast Packet

1 sec

If the average per second of multicast packets in the last 20 seconds >= sensitivity

Duplex mismatch HDx

6

21

36

1/10,000 Outgoing

20 sec

If (late collisions/total) >= (sensitivity/10,000)

Duplex mismatch FDx

6

21

36

1/10,000 Incoming

20 sec

If (CRC and alignment errors/ total) >= (sensitivity/10,000)

Link flap — Excessive transitions between link-up and link-down states.

4

7

11

One Transitions

10 secs

If the Transition count in the last 10s >= sensitivity.

Example: of sensitivity calculation:

If a sensitivity is set to High, and a bad cable is causing 15 CRC errors out of a total of 3500 packets transmitted in a 20 second period:

  1. CRC errors/total must be >= (sensitivity/10,000) to trigger an alert.

  2. CRC errors/total = 15/3500 = .00043

  3. Sensitivity/10,000 = 6/10,000 = .0006

  4. .00043 is not greater than or equal to .0006, so an alert is not triggered.