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Wrong Packets Accumulated at the Gigabit POS Interface of the NE20 Connected to the S2016

Publication Date:  2012-07-27 Views:  143 Downloads:  1
Issue Description
During a routine inspection at an office, the engineer found that a great number of wrong packets accumulated at the Gigabit optical interface of the NE20 that was connected to the S2016 and the number of wrong packets kept increasing, but no wrong packets existed at the Gigabit optical interface of the S2016.
GigabitEthernet1/0/1 current state: UP
Line protocol current state: UP
Description: To_S2016-A
The Maximum Transmit Unit is 1500 bytes
Internet Address is
Internet Address is Sub
IP Sending Frames’ Format is PKTFMT_ETHNT_2, Hardware address is 0018-8257-96cf
Hardware is GigabitEthernet
VendorName: AVAGO
Compliance: 1000BASE-SX
PartNumber: HFBR-5710L
Mode: MultiMode
LaserwaveLen: 850
Length for 50/125um: 550m
Length for 62.5/125um: 270m
Output queue: (Urgent queue: Size/Length/Discards) 0/50/0
Output queue: (Protocol queue: Size/Length/Discards) 0/1000/0
Output queue: (FIFO queue: Size/Length/Discards) 0/256/0
no auto negotiation, speed 1000M, duplex full, loopback not set
Statistics last cleared: never
Traffic statistics:
Last 300 seconds input rate 2504 bits/sec, 3 packets/sec
Last 300 seconds output rate 1600 bits/sec, 1 packets/sec
Usage of input bandwidth:0.00%,Usage of output bandwidth:0.00%
Input: 35971860 packets, 38285801016 bytes
120990 broadcasts, 51000 multicasts, 0 pauses
0 InvalidVlanPkts, 0 InvalidVlanOctets
232372 errors, 0 shorts, 0 longs
232372 physical errors, 0 input fragments
0 Jabbers, 0 CRC, 0 overruns
Output: 30384013 packets, 25175997197 bytes
10102 broadcasts, 877400 multicasts
0 InvalidVlanPkts, 0 InvalidVlanOctets
0 shorts, 0 longs
0 runts, 0 Jabbers, 0 CRCs
0 deferrals, 0 underruns, 0 aborts
0 collisions, 0 lates, 0 singles, 0 multiples, 0 excessives 

Alarm Information
Handling Process
According to the analysis of the packets captured through mirroring from the interfaces on the NE20 and the S2016:
1. Because the device did not meet the condition for on-site capturing of packets, the engineer simulated the interconnection between the NE20 and S2016 with the Gigabit link in the lab.
2. The packets were captured from the Gigabit optical interface of the NE20 for analysis.
Because the accumulation of wrong packets was caused by the inability of the NE20 to identify STP packets, the services would not be affected. No special measures needed to be taken to address the problem. 

Root Cause
This was because the Gigabit optical interface of the NE20 could not identify the following packets. There was nothing wrong with the S2016:
1. STP packets
2. The HGMP packets with 0x88a7 as the protocol number
3. The 3com packets with 0x9001 as the protocol number
The statistics were mostly about the wrong STP packets, approximately 1 packet a second. Because the NE20 does not support Layer 2 features and cannot identify STP packets, a large number of wrong packets accumulate at the Gigabit optical interface of the NE20. 

If the accumulation of wrong packets at the port is caused by the inability of the NE20 to identify STP packets and the services are not affected, you do not need to take measures to address the problem. It is recommended to enable the NE20 to identify the STP packets in later versions.