Receiving FCS-Err on Cisco catalyst 6500

[sharma.advait]

When I am checking Sh Port on Cisco Catalyst 6500 I am getting FCS-Err 18360 on port 3/1.

Port 3/1 is connected with another Catalyst 6500 through single mode fiber on another location.

I am facing ping break issues and slow network complains from user.

[Hitesh Vinzoda]

Hi,

This is typically a physical issue (such as cabling, a bad port, or a bad Network Interface Card (NIC)) but can also indicate a duplex mismatch.

HTH

Hitesh Vinzoda

Pls rate useful posts.

[rajatsetia]

Hi,

When operating at full-duplex, FCS, cyclic redundancy checks (CRC), alignment errors, and runt counters should be minimal. If the link is operating at full-duplex, the collision
counter is not active. If the FCS, CRC, alignment, or runt counters are incrementing, check for a duplex mismatch. Duplex mismatch is a situation in which the switch is
operating at full-duplex and the connected device is operating at half-duplex, or the other way around. The result of a duplex mismatch is extremely slow performance,
intermittent connectivity, and loss of connection. Other possible causes of data link errors at full-duplex are bad cables, a faulty switch port, or NIC software or hardware
issues.

Documentation:
http://www.cisco.com/en/US/customer/products/hw/switches/ps700/products_tech_note09186a008
015bfd6.shtml

FCS is layer 1 issues and few general causes are

- Mismatch of SFP type on both ends

- Dirty fiber connector or SFP

- Faulty termination of fiber

- Mismatch in cable type i.e. patch cable is different from optical fiber running between patch panels

- Mismatch of duplex

Troubleshooting

- try switchport nonegotiate

- hardcode the duplex setting to full

- try using different SFP or switch ports

- use optical TDR to test the end to end connectivtiy

Hope it helps

Kind Regards,