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Incorrect configuration of MA5100 results in unsuccessful ping at the beginning of interconnecting with the N1EFT8 board of the OSN 2500 equipment

Publication Date:  2012-07-24 Views:  75 Downloads:  0
Issue Description
The 10G equipment and the 2500 equipment form a ring network and provide Ethernet services to each other. The external device of the EFS4 board of the 10G equipment pings the MA5100 interconnected with the peer EFT8 board. The ping fails at first and needs a long period of retry before success (in this network, the EFT8 board of the 2500 equipment is interconnected with the MA5100).      
Alarm Information
Handling Process
1. By capturing packets between MA5100 and the EFT8 board, we find MA5100 gives no response after the EFT8 board sends out the ping message.
2. By checking the configuration of MA5100, we find cell VLAN is configured. Modify the configuration, and the problem is solved.       
Root Cause
Since the ping operation fails at first and then succeeds later, we suspect the problem is related to the interconnected devices. In the pinging process, the ICMP first sends an ARP message to interpret the MAC address of the peer device. The two ends can be ping through only when the peer MAC address is successfully interpreted. A further analysis concludes that during configuration of cell VLAN, BASE sends an ARP message to the LAND board of MA5100. And the LAND board treats it as an unknown unicast and cannot broadcast it to the SCC board. As a result, the SCC board of the MA5100 equipment cannot return the MAC address to the BASE device on an upper layer, Then, the ping operation fails.
At this time, the equipment returns its MAC address to the downstream MA5100 and the BASE equipment learns the MAC address. In this way, the ping operation succeeds. The MA5100 equipment sends the ARP message on a regular basis of 20 minutes. When the system starts to operate, the time is counted. Thus, the ping operation succeeds after a while.
After a period, due to the aging of the MAC address, the upper layer switch cannot learn the MAC address of the lower layer MA5100 device when the ping is attempted. Therefore, the procedure above is repeated, and the ping operation fails.