CRC/FCS errors on 10G links between MikroTik CRS switches and Cisco Catalyst 3750-X/2960-S

Question

The poster runs temporary event networks and has twice hit heavy frame errors on 10G links between MikroTik and Cisco switches. About a year earlier a Cisco Catalyst 2960-S with 10G uplinks connected to a MikroTik CRS317-1G-16S+ showed CRC errors on the Cisco side and swapping cables did not help. At the current event a Catalyst 3750-X with a 10G module connected to a MikroTik CRS326-24S+2Q+RM shows FCS errors all over the place on the MikroTik side. The DAC had already been replaced by a brand-new fiber patch cord with two new SFP+ modules without improvement. The poster asked what to consider when negotiating such a cross-vendor 10G link.

Hardware: Cisco Catalyst 3750-X with 10G network module, Cisco Catalyst 2960-S with 10G uplinks, MikroTik CRS326-24S+2Q+RM, MikroTik CRS317-1G-16S+
Transceivers: unspecified 10G SFP+ DAC, unspecified 10G SFP+ optics (new pair)
Form factor: SFP+, DAC

Symptoms / messages:

CRC errors on the Cisco 10G port
FCS errors on the MikroTik side
errors persist after replacing DAC with a new patch cord and new SFP+ modules

coreguru · Answer

Usual layer-1 suspects here: a bad 3750-X port, a bad cable, bad frames from the peer, or NIC/SFP incompatibility between MikroTik and Cisco. I'd hard-code the port settings on both devices instead of relying on negotiation, and for third-party optics try the Cisco commands 'service unsupported-transceiver' and 'no errdisable detect cause gbic-invalid'.

opticnerd31 · Answer

Before I can diagnose this, I need the SFP+ model, the exact switch model and IOS version, plus 'show version', 'show logging', 'show run interface', 'show interface' and 'show interface transceiver' output.

wavesmith · Answer

I doubt the CRS326-24S+2Q+RM even supports 10G. Can you post a photo of the setup?

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