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The NE20 Receives a Large Number of Broadcast Packets When It Is Connected to the OSN1500B

Publication Date:  2012-07-27 Views:  188 Downloads:  0

Issue Description

 The networking is as follows:
NE20--OSN1500B-----Transmission fiber----OSN1500B--NE20
/ \
Transmission fiber Transmission fiber
/ \
NE20--OSN1500B OSN1500B-----NE20
The OSN1500Bs are physically connected in a star topology and logically fully meshed.
After the OSN1500Bs and the NE20s are interconnected, the interfaces on the NE20s receive a large number of broadcast packets.
Input: 1271894 packets, 1935756888 bytes
1271848 broadcasts, 46 multicasts, 0 pauses
0 InvalidVlanPkts, 0 InvalidVlanOctets
0 errors , 0 shorts, 0 longs
0 physical errors, 0 input fragments
0 Jabbers, 0 CRC, 0 overruns
Output: 7137 packets, 4317192 bytes
37 broadcasts, 7100 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
E-VLAN services are configured on the OSN1500Bs. One VB is configured with five VCs, and in the VLAN filtration view, five VCs are set to transparently transmit frames from the same VLAN. 


Alarm Information



Handling Process

 1. Check the interfaces on the NE20s that connect to the interfaces on the OSN1500Bs. It is found that the interfaces on the NE20s receive a large number of broadcast packets but send a few packets. Shut down all the interfaces on the NE20s and then run the undo shutdown command on the interfaces on the NE20 at a site. The interfaces still receive a lot of broadcast packets. This indicates that the broadcast packets are not generated on the NE20s.
2. After STP is enabled on the OSN1500Bs, no more broadcast packets are generated. This means that a loop is formed on the connected links. Analyze the configurations of the OSN1500Bs and consult engineers of the optical network. It is found that one VB configured with five VCs functions as a switch, that is, these five VCs can communicate with each other. When the five virtual links communicate with the same interface on an NE20, a loop occurs.
To address the problem, we configure five VLANs on the interface on the NE20, and then enable five sub-interfaces on the connected interface to terminate the VLAN tag. At the same time, five VCs are bound to five VLANs respectively in the T2000 Ethernet configuration view. 


Root Cause

 1. The OSN1500Bs generate a large number of broadcast packets.
2. Ethernet interfaces on the OSN1500Bs are incorrectly configured or interfaces on the NE20s are incorrectly configured.