CRC Error Threshold

[ash93]

Hi,

We were conducting some simulations using Huawei switch and Cisco switch. We observed that the Huawei switch is detecting CRC errors for video multicast output, while the Cisco switch is not detecting any CRC errors.

Cisco Switch Model: CATALYST 3850 (48 Port 1G)

Is there any threshold setting/configuration for Cisco switch for CRC error detection?

Thank you. 

[DanielP211]

Hello!

If CRC errors are happening you will see them in show int gig1/0/X... Are you sure you don't have an issue with Huawei or any cabling between huawei and the end device?

BR

[ash93]

Hi Daniel, 

I m able to see the CRC errors in a specific port. With the same cabling, we try to retest with Huawei switch, it is able to detect CRC errors. 

Just wondering if there is any threshold set in Cisco switch that does not show any minor issue? 

[Giuseppe Larosa]

Hello @ash93 ,

to be able to detect CRC errors a switch needs to work in store and forward if it uses cut through or other modified versions of cut through it cannot.

https://www.networkacademy.io/ccna/ethernet/store-and-forward-vs-cut-through-switching

so the question is how to understand what switch mode is used in the Cisco device.

from Catalyst 3850 datasheet

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-3850-series-switches/data_sheet_c78-720918.html?dtid=osscdc000283

>>Audio video bridging

With Cisco IOS^® XE Software Release 16.3, Cisco Catalyst 3850 Multigigabit and 3850 10G SFP+ now support the IEEE 802.1 AVB standard. This standard provided the means for highly reliable delivery of low-latency, time-synchronized AV streaming services through Layer 2 Ethernet networks. The standard also makes it easier to integrate new services and for AV equipment from different vendors to interoperate. Whether the AV endpoint connections are analog or are inflexible digital one to one, the network transport enables many-to-many transparent plug-and-play connections for multiple AV endpoints.

and

https://en.wikipedia.org/wiki/Audio_Video_Bridging

Hope to help

Giuseppe

[ash93]

Hi @Giuseppe Larosa, i m unable to find what is the switching-mode configured. There is no such command as show switching-mode. From what i read online, the default configuration for access port is store and forward (switchport mode access) . But does this mode determines the CRC error noticed in the switch port? 

[Giuseppe Larosa]

Hello @ash93 ,

>> But does this mode determines the CRC error noticed in the switch port? 

yes with store and forward the switch receives the whole frame checks the FCS checksum to detect possible errors and CRC errors are originated by a mismatch between the locally calculated checksum ( a 32 bit field ) and the FCS attached to the received frame.

In cut through mode the switch starts to send the frame on the outgoing port as soon as it receives it.

Modified cut through waits for receiving 64 bytes before sending out the frame on the outgoing interface  (64 byte is the minimal size of an Ethernet frame)

Usually these are hardware design choices. if the switch 3850 works in store and forward switching mode it should be able to detect CRC errors so the suggestions made by @DanielP211 apply.

Hope to help

Giuseppe