09-26-2022 06:17 AM
Hello All,
Is the generally acceptable level of CRC errors on a device 1% or less, or does it vary depending on the device type, e.g. router vs. switch vs. WLC? I have an NCS 5500 that is slowly accumulating CRC's, at an extremely low rate, and I don't think it is an issue. Works out to be 0.0000284979936 percent. Output below.
sh int TenGigE0/0/0/47
TenGigE0/0/0/47 is up, line protocol is up
MTU 9216 bytes, BW 10000000 Kbit (Max: 10000000 Kbit)
reliability 255/255, txload 2/255, rxload 4/255
Full-duplex, 10000Mb/s, ER, link type is force-up
Last link flapped 3w6d
Last input 00:00:00, output 00:00:00
Last clearing of "show interface" counters 2d08h
30 second input rate 162918000 bits/sec, 14852 packets/sec
30 second output rate 112550000 bits/sec, 30847 packets/sec
9351535528 packets input, 13487753442521 bytes, 0 total input drops
Received 0 broadcast packets, 241380 multicast packets
8 runts, 0 giants, 0 throttles, 0 parity
2684 input errors, 2676 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
09-27-2022 04:05 AM
Hi
I agree with you, this is a "no issue", as the fault rate is so extremely low.
If this is an fiber connection, and you got an chance sometimes, (on a service window) you may try to clean the fiber patches, and see if the errors disappear.
/Mikael
09-27-2022 02:44 PM
"Is the generally acceptable level of CRC errors on a device 1% or less"
There an old rule-of-thumb, that TCP, well at least for old bulk data transfers, considered an error rate of 1% or less, "acceptable"; don't recall such a rule for CRC errors, though. I.e. A CRC error rate of 1% might be considered very "high".
Actually, different media specs, I believe, have an "expected" bit error rates, like 1 bit error somewhere in the range of 10E12 to 10E20. Do note, that a single bit error will likely cause a CRC error (BTW, there's not 100% error detection; CRC algorithms have their own "quirks") for whatever group of bits the CRC is being applied to, like a Ethernet frame. (I also believe bigger blocks will raise the overall CRC error percentage, although I also recall "too large" blocks impact CRC error detection - the mathematics behind CRCs make my head hurt - laugh.)
If you can find the expected BER spec for your media, based on the number of bits per your averaged sized CRC "block" (e.g. frame/packet), you should be able to compute an expected CRC error count.
NB: Also BTW, there are different CRC algorithms, that are used for different media, to best detect bit errors on that media.
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