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Sequence-Err on Catalyst 4948-10GE Fiber Links

Hello all,

we have multiple Video production networks, with Video servers (AVID Unity ISIS) connected by 10GE fiberlinks to 4948-10GE switches. On almost every of these switches, I see more or less "Sequence-Err" interface errors.

We do not currently have a known problem because this, and no other errors are seen!!!

But I would like to understand the error, and therefore I would like to find out, what a sequence error means, what the cause is, and what the impact (to a frame) is?

By the way, it is well-known that the ISIS Video server does generate very excessive UDP data bursts. Mybe this matters?

On Cisco doc I did not find an answer. The document "Troubleshooting Switch Port and Interface Problems" does unfortunately not refer to "sequence-err".

Here is an example output:

WS-C4948-10GE#sh int t1/49

TenGigabitEthernet1/49 is up, line protocol is up (connected)

  Hardware is Ten Gigabit Ethernet Port, address is 0026.cb38.e030 (bia 0026.cb38.e030)

  Description: ISIS-VLAN-1

  MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec,

     reliability 255/255, txload 3/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 10Gb/s, link type is auto, media type is 10GBase-SR

  input flow-control is on, output flow-control is off

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input never, output never, output hang never

  Last clearing of "show interface" counters never

  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  30 second input rate 28777000 bits/sec, 2589 packets/sec

  30 second output rate 139716000 bits/sec, 11970 packets/sec

     129865159126 packets input, 178954080407901 bytes, 0 no buffer

     Received 349957520 broadcasts (132318066 multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 input packets with dribble condition detected

     37205852859 packets output, 33235281073128 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

WS-C4948-10GE#sh int t1/49 counters errors

Port       CrcAlign-Err Dropped-Bad-Pkts Collisions   Symbol-Err

Te1/49                0                0          0            0

Port          Undersize  Oversize  Fragments      Jabbers

Te1/49                0         0          0            0

Port         Single-Col Multi-Col   Late-Col   Excess-Col

Te1/49                0         0          0            0

Port       Deferred-Col False-Car  Carri-Sen Sequence-Err

Te1/49                0         0          0         2639

Thank you in advance!


InayathUlla Sharieff
Cisco Employee

Hi Hakan,

Sequence-Error are equal to FCS error:

The number of valid size frames with Frame Check Sequence (FCS) errors but no framing
errors. This is again typically a physical issue (such as cabling, a bad port, bad Gbic or
a bad Network Interface Card (NIC)) but can also indicate a duplex mismatch.



Hello Inayath,

thank you. I already knew FCS errors, but I was not sure, if a sequence error is the same. Because on other Catalyst models they are identified clearly as "FCS-Err" errors.

However, it seems that the question about the cause and the relation to the serverports remains. Because the described causes do not match to our problem. The error is observed on different switches, on different locations, but only on those specific serverports, and it is very unlikely that all these cables or NICs are broken, and duplex is for sure not an issue.

Anyway, many thanks!

Kind regards